
Qass. 
Book. 



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IHsserthiion Third 



[? i v: I i ; ^s OF CHK \rT< : V 1. FHTT-OSOPR V 



1 TnpOMA^" RHAVIM 



KV \\ 1,1.1, S 




SI f""^ 



DISSERTATION THIRD : 



EXHIBITING A GENERAL VIEW OF THE 

pjrogress of CI)emical pi^ilosopl^p, 



PROM THE EARLY AGES TO THE END OF THE 
EIGHTEENTH CENTURY. 



BY WILLIAM THOMAS BRANDE, 

Secretary of the Royal Society of London, Fellow of the Royal Society of Edinburgh, 
Professor of Chemistry in the Royal Institution of Great Britain, and Pro- 
fessor of Chemistry and Materia Medica to the Society of 
Apothecaries of the City of London. 






DISSERTATION THIRD, 



SECTION I. 



GENERAL VIEW OP THE PROGRESS OP CHEMICAL SCI= 
ENCE, PROM THE EARLY AGES TO THE END OF THE 
SEVENTEENTH CENTURY. 



The phenomena of the universe present a series of 
changes, of which the regularity and harmonious succes- 
sion excite the surprise of superficial observers, and awaken 
the admiration and attention of the philosophick mind. 

These changes are either accompanied by visible motion 
susceptible of measurement, and relate to the exterior forms 
and mechanical characters of bodies, or they depend upon 
the mutual agencies of the elementary principles of matter, 
upon its composition, upon its susceptibility of acquiring 
new properties by entering into new combinations. 

The investigation of the former phenomena belongs to 
the mechanical philosopher ; to trace the causes of the 
latter, and to discover the laws to which they are obedient, 
is the business of Chemical Science.* 

^ Dtfinitions of Chemistry, — "La Chymie est ua art qui en- 
seigne a separer les di^erentes substances qui se rencontrent dans 
un mixte." (L'Emery, Cours dc Chymie.) 



4 THIRD DISSERTATION. [skct. i. 

Chemistry, considered as a branch of scientifick inquiry, 
is not of ancient date.^ Founded upon principles deduced 

" Chemistry is that science which examines the constituent 
parts of bodies, with reference to their nature, proportions, and 
method of combination." (Bergman, Essay on the Usefulness 
of Chemistry,) 

" Chemistry is the study of the effects of heal and mixture? 
with a view of discovering their general and subordinate laws, 
and of improving the useful arts." (Black, Lectures.) 

" La Chimie est une science qui apprend a connaitre Taction 
intime et reciproque de tous les corps de la nature, les uns sur 
les autres. Par les mots action intime^ et reciproque^ cette sci- 
ence est distinguee de la physique experimentale, qui ne consi- 
dere que les proprietes exterieures des corps doues d'un volume, 
et d'une masse quon pent mesurer, tandis que la Chimie ne 
s'attache qu'aux proprietes inlerieures, et n'agit que sur des mo- 
lecules, dont le volume et la masse neu peuvent pas ^tre soumis 
aux mesures et aux calculs." (Fourcroy, Systeme des Connois- 
sance Chimiques^ Vol. I. p. 4.) 

'* Die Chemie ist eine Wissenschafl die unsdie wechselseitige 
wirkungen der einfachern Stoffe in der Natur, die zHsammen- 
setzung der korper aus ihren und nach ihrdn verschiedenen ver- 
haltnissen, und die Art und Weise kennen lehrl, sie zu trennen, 
Oder sie wieder zu neuen Korperarten zu verbiuden." (Gren. 
Systematisches handbuch der Chcmie, p. 1. Halle, 1794.) 

** Chemistry is that science which treats of those events or 
changes in natural bodies, which are not accompanied by sen- 
sible motions." Thomson, System of Chemistry^ fifth edition, 
p. 2.) 

Most of the substances belonging to our globe are constantly 
undergoing alterations in sensible qualities, and one variety of 
matter becomes, as it were, transmuted into another. Such 
changes, whether natural or artificial, whether slowly or rapidly 
performed, are called chemical; — thus the gradual and almost 
imperceptible decay of the leaves and branches of a fallen tree 
exposed to the atmosphere, and the ra()id combustion of wood in 
our fires, are both chemical operations. 

" The object of chemical philosophy is to ascertain the causes 
of all phenomena of this kind, and to discover the laws by which 
they are governed." (Davy, Elements of Chemical Philosophy, 

p. 1.) 

In the edition of Johnson's Dictionary y now publishing by the 
Rev. H. J. Todd, the erroneous and antiquated definition of 
Boerhaave is very improperly retained. " An art whereby 



SECT. 1.} THIRD DISSERTATION, 5 

from experiment and observation, centuries were consumed 
in their accumulation and systematic arrangement ; but, as 

sensible bodies contained in vessels, or capable of being contain- 
ed therein, are so changed by means of certain instruments, and 
principally fire, that their several powers and virtues are thereby 
discovered, with a view lo philosophy or medicine." 

The derivation of the word Chemistry can scarcely be said to 
have been ascertained. The most plausible guesses are the fol- 
lowing : from yyo) to melt, or ;^t;/wd? juice ; from kema, an oriental 
word signifying black ; from ;tj«^}j5. the name of a person emi- 
nently skilled in the sciences; fiom CMmi, the Co[)tick name of 
Egypt, where the art is supposed to have had its rise. 

According to Bryant [Ancient MythoL), it is derived from che- 
mia^ and that word from Cham, 

The Rev. Mr. Palmer, Professor of Arabick at Cambridge, has 
given the following etymology : '' Al-chemy, or more properly 
Al-kemy, the knowledge of the substance or composition of 
bodies, so named from the substantive (Kyamon,) that is, the 
substance or constitution of any thing ; from the root (Kama.) 
Golius. Lexicon.''^ (Thomson's Chemiatry, 5th edit. p. 4. Note.) 

Conversing upon this subject with Dr. Thomas Young, he re- 
marked, that the Egytians probably neither knew nor cared 
much about the composition of bodies; and the term of Chemis- 
try, as referring to the secret art of transmutation, was ]>robably 
derived from the Coptick vooXlihcms or chcms, signifying obscure^ 
dark. The German word geheim, secret, he said, was perhaps of 
the same root. 

" Haec ars varia accepit nomina, nam omnium primo dicta 
fuit Tixyvi ^ofviTiKvif et antiquis illis temporihns per banc signitica- 
bant artem vilia metella in aurum convertendi, et ejus artifices 
'^rotnrxi vocari Zozimus dicit. Veteres Aegyptios banc artem 
Chimoct vocasse Josephus Scaliger ibi ostendit, std poslea Grae- 
ci hanc artem ;i^^i;o-o5ro/i3«r<y dixerunt, Arabibus vero, Alchcmia.'^ 
(Boerhaave, {Instiiutioncs Chemiae,) 

' "Tout ce qu'on a dit de Tantique origine de la Chimie, sur 
les premiers hommes qui ont travaille les metaux, taille et poli 
les pierres dures, fondu les sables, dissous et crystallise les seLs, 
ne montre a un esprit exact et severe qn'une vaine et ridicule 
pretension, semblable acette par laquelle on voudrait riconnoi- 
fre les el6mens de la geometrie 4lans Touvrage grossier du sauvage 
qui use les fragmens du rocher, qui lour donne des formes a pen 
pres regulieres pour les rendre utiles a ses [)remiers besoius.'^ 
(Fourcroy, Discours Priliminaire.) 



6 THIRD DISSERTATION. [sect. i. 

an art, cheaiistry is readily traced to periods of remote an- 
tiquity ; for it is obvious that the chemical changes of mat- 
ter must have been rendered subservient to the wants of 
mankind in the earliest ages of the world. 

Metallurgy is among the most ancient of the arts, and 
Tubal Cain, the instructor of workers in iron and brass, 
has thence been called the inventor of chemistry. Others 
have preferred the claims of Noah, to whom the invention 
of wine has been attributed ; but these, and other arts allud- 
ed to in Sacred Writ, such as dyeing, gilding, and em- 
balming, which have been adduced as instances of chemi- 
cal knowledge in the time of Moses, prove nothing more 
than that such processes were practised at that period, in- 
dependent of each other, and quite unconnected by the 
slightest reference to general principles.^ 

It is probable that the early mythological systems of the 
Egyptians contained some allusions to the chemical chan- 
ges of matter, and to them the first speculations on the art 
of transmutation have been attributed. Hermes, or Mercu- 
rius Trismegistus, the favourite minister of the Egyptian 
king Osiris, has been celebrated as the inventor of this art, 
and the first treatise upon it has been attributed to Zosy- 
mus, of Chemnis or Panopolis in Egypt. The inhabitants 
of Sidon and Tyre, those renowned seats of the commerce 
of the ancient world, seem to have been skilled in some 

^ " Si Ton examine cependant avec courage et sans prejuge 
toutes les preuves qu'on a reunies pour etablir Texistence de la 
Chimie chez les Egyptiens, apres avoir reporte son origine aux 
premiers ages du monde, et aux premiers travaux ou les hommes 
ont em\.\oye le feu comme agent, on reconnait bientot que tirees 
uniquement des products employes dans leurs constructions di- 
verses, elles peuvent toules annoncer des arts ou des precedes de 
fabrique plus on moins avances raais rien qui tienne a des no- 
tions generales lirees de ces arts compares, rien qui depende 
d'une doctrine s!jivie, rien eofin qui puisse douner uneideed'une 
veritable science " (Fourcroy, Disc. PreL) 



SECT.i.] THIRD DISSERTATION. 7 

chemical manufactures ; they made glass and artificial gems, 
and excelled in dyeing purple. 

Egypt maintained its superiority in arts until the inva- 
sion of Alexandria by the Saracens, when the celebrated 
library collected by the Ptolemies, with great diligence and 
at enormous expense, was burned by the orders of the Ca- 
liph Omar.' The alchemical works had been previously de- 
stroyed by Diocletian in the fourth century, lest the Egyp- 
tians should acquire by such means sufficient wealth to 
withstand the Roman power. On the present occasion, 
about seven hundred thousand volumes were seized, which 
we are told supplied six months fuel for forty thousand 
baths, that contributed to the health and convenience of the 
populous capital of Egypt. 

When philosophy declined in Egypt and in the East, 
Greece became the principal seat of learning and of the 
arts ; but the system of theirearly philosophers, of Thales^ 
the founder of the lonick sect, of Anaximander, and Anaxi- 
menes, breathe the sentiments of the Egyptian schools. 
By Thales, water was considered as the source of all things, 
as the universal element. The opinions of Anaximander, 
in themselves unintelligibly obscure, received some eluci- 
dation from his successor Anaximenes ; they regarded air 
and fire as the first rudiments of matter. 

The result of the Macedonian war introduced Grecian 
philosophy into Italy, and the doctrines of Plato,^ and 
Aristotle, and Theophrastus, prevailed in the school of 
Rome. 

Among the early Roman philosophers, Lucretius* stands 
preeminent ; but his opinions had been formed at Athens, 

* " Qui his scriptis parcendura esse negabat, quippe quae inu- 
tilia essent, si eorum dogmata Alcorano coogruerent, noxia vero 
si ab illo dissentirent." (Bergman, De primordiis C/icmiac.) 

^ 500 years B. C. ^ 340 years B. C. ' 50 years B. C. 



8 ^ THIRD DISSERTATION. [srct. s. 

in the Stoick school of Zetio, and he early imbibed the 
doctrines of Empedocles and Epicurus, which are expound- 
ed with superiour genius and admirable ingenuity in his 
masterly poem on the Nature of Things. 

The celebrated Natural History of the elder Pliny, writ- 
ten in the first century of the Christian era, contains an ac- 
count of the rise and progress of the arts and sciences pre- 
vious to that period, which, though not always accurate, 
often obscure, and sometimes unintelligible, abounds in in- 
structive documents and interesting remarks. It is written, 
not in the elevated, refined, and elegant style of the Au- 
gustan age, but in the language of the laborious and liberal 
historian, frequently led by the extent of his inquiries to 
subjects which he is incompetent to manage, and upon 
which his opinions are incorrect, his conjectures vague, his 
assertions ill founded. 

The origin of many of the follies and mysteries of Al- 
chemy may perhaps be referred with most propriety to 
the New PlatonistSy whose rise marked the declining age 
of learning towards the end of the third century of the 
Christian era. These philosophists, celebrated for their 
metaphysical disputes and superstitious notions, credited 
the existence of demons and spirits, with whom they claim- 
ed familiar intercourse. Neglecting useful knowledge, they 
exhausted their strength in verbal disputes, and in attempts 
to discover the secrets of the invisible world ; thus gradu- 
ally converting the study of philosophy into that of de- 
monology and magick. " Several of these masters,'' says 
Gibbon, " Ammonius, Plotinus, Amelius, and Porphyry, 
were men of profound thought and intense application : 
but, by mistaking the true object of philosophy, their la- 
bours contributed much less to improve than io corrupt 
the human understanding." 



SBCT. I.] THIRD DISSERTATION. 9 

Porphyry died about the time of Diocletian's abdication. 
The life of his master, Plotiniis, which he composed, gives 
a complete idea of the genius of the sect, and the manners 
of the Professors. This curious piece is inserted in Fabri- 
cius. {Bibliotheca Graeca, Tom. IV.) When the culti- 
rated part of Europe was overwhelmed by the barbarous 
nations, all records of arts and sciences possessed by the 
Greeks, and by their Roman successors, were swept away 
in the general destruction, and now the Arabians became the 
protectors of philosophy, and the promoters of its pursuits. 
To them, Chemisfry, regarded as a distinct branch of ex- 
perimental philosophy, owes its origin, and several circum- 
stances co-operated to render its progress rapid, which are 
important in their relation to the subsequent advances of 
the science. Among these the mysteries of Alchemy, so 
well adapted to the genius of that age and people, are the 
most remarkable. Of this occult art, the two leading ob- 
jects were the transmutation of common metals into gold 
and silver, aud the discovery of the universal medicine, 
which, by the removal and prevention of disease, should 
confer immortality upon the possessors of the secret. 

The origin of these chimerical notions has been various- 
ly accounted for. The idea of transmutation may plausibly 
be referred to the various processes to which natural bodies 
were submitted by the astrological experimentalists of the 
seventh and eighth centuries. Observing the change of 
properties in metalick ores by exposure to heat, and the pro- 
duction of malleable and useful metals from their brittle and 
useless compounds, it is not surprising that superficial ob- 
servation and incorrect reasoning should lead to a belief in 
(heir production and transmutation ; and such speculations, 
not without apparent foundation, holding out attraction to 
the ambitious, and hope to the needy, would soon excite 



10 THIRD DISSERTATION. [sect, i 

notice, and coomiand followers. That this was the case, 
the records of those times amply testify- 

The pursuit of the other object may be referred to the 
success attending the medical employment of many of the 
chemical preparations. Pharmacy was becoming enriched 
by the introduction of chemical compounds ; and remedies 
for diseases, before deemed incurable, were occasionally dis- 
covered among the products of the furnace. Hence, per- 
haps, the possibility of the existence of an universal reme- 
dy might occur to those under the infatuations of the black 
art. 

The earliest of the true Alchemists, whose name has 
reached posterity, is Geber,* supposed to have been an Ara- 
bian prince of the seventh century. The works attributed 
to Geber, several of which have been published in Latin 
translations by Golius, and others in English by Russell, 
are numerous and curious. They abound in the cant and 
jargon of the hidden art. Some have asserted his preten- 
sions to the possession of the universal medicine, for he 
speaks of curing disease. But this seems a mere meta- 
phorical expression, relating to transmutation. *' Bring 
me," says he " the six lepers, that I may cleanse them ;" 
by which he doubtless would imply the conversion of silver, 
mercury, copper, iron, tin, and lead, into gold, — there be- 

* " Primus omnium Arabum post Graecos est Geher, cui dant 
titulum Arabis. Alii dicunt eum fuisse regem, unde rex Gcber 
Arabs, dici solet ; sed Leo Africanus. qui Graecus fuit et multa 
descripsit ex antiquis Arabibus, dicit, Gebrum ilium natione Grae- 
cus fuisse, sed dero^^asse suam religionem, et se dedisse Mahorae- 
dae religion! Arabum, et vixisse septirao seculo." (Boerhaave.) 

Geber was also a physician and astronomer. The following 
are the principal works on Chemistry, which have been attributed 
to him ; De Alchemia, — De sinnmd perfectione Metallorum, — De 
Lapide Philosophico, — De inveniendi arte Auri et Argenti, These, 
and some other works bearing his name, whether genuine or not, 
furnish good specimens of the early alchemical writings. 



swT. ,.] THIRD DISSERTATION- 11 

ing only these seven metals known at that period. Dr. 
Johnson supposes that the word Gibberish^ anciently writ- 
ten Geberishy was originally applied to the language of Ge- 
ber and his tribe. 

The elder Mesne and Avicenna/ physicians of the ninth 
and tenth centuries, have given some account of the Che- 
mistry of their age, but their works relate chiefly to medi- 
cine. Indeed, it is probable, that the writings now extant 
in the name of the former are spurious. 

The twelfth, thirteenth, and fourteenth centuries, abound 
in writers on the secrets of Alchemy ; and the happy few 
to whom fate and metaphysical aid had granted the discov- 
ery of the great secret, assumed the title of adepts, a charac- 
ter which required to be sustained by superiour feats of de- 
ception and duplicity. 

About this period, several circumstances happily concur- 
red, favourable to the diffusion of learning and the arts, which 
began again to dawn in Europe with promising splendour. 

The extravagant expeditions of the Crusaders tended, in 
these respects, to the most extensive, beneficial, and per- 
manent consequences. In their progress to Palestine, 
these ardent followers of the Cross traversed countries 
which, compared with their own, were cultivated, civilized, 
and refined. Their minds and manners were thus enlarged 
and improved, and new customs and institutions attracted 
their notice. 

In Constantinople, then the largest and most magnificent 
of European cities, some traces of ancient elegance and 
refinement were still to be found, and many of the natural 

* Avicenna introduced several important drugs into the Ma- 
teria Medica ; and the art of making sugar has been enumerated 
among his discoveries, although, doubtless of earlier date. 



12 THIRD DISSERTATION. [sect, l 

products and of the manufactures of the East were oflfered 
to their notice/ 

We accordingly discover in these superstitious and en- 
thusiastick expeditions the source of many improvements, 
which afterwards raised Europe to the highest rank among 
nations ; which tended to dispel barbarism, to mitigate the 
fury of war, and to extend commerce ; and which ulti- 
mately led to the cultivation of the useful and fine arts, and 
to the diffusion and exaltation of science. 

Another event occurred about this period, which mira- 
culously facilitated the acquisition and propagation of 
learning, namely, the invention of printing, which, as it 
were by superhuman mediation, advanced so rapidly to 
perfection, that the finest specimens of typography are to 
be found among the early efforts of the art. It was intro- 
duced into England by the Earl of Rivers, in the reign of 
Edward IV.^ 

Of the earlier writers on Chemistry, no one is more de- 
serving notice than the celebrated Roger Bacon, a native 
of Somersetshire, who flourished in the thirteenth century. 
His writings, though troubled and polluted by the reigning 
absurdities of Alchemy, contain many curious facts and 
judicious observations. To him the discovery of gun- 

' " The first and most obvious progress was in trade and 
manufactures, — in the arts, which are strongly prom})ted by the 
thirst of wealth, the calls of necessity, and the gratification of 
the senses or vanity. Among the crowd of unthinking fanaticrks, 
a captive or a pilgrim might sometimes observe the sui)eriour 
refinement of Cairo and Constantinople. The first importer of 
windmills was the benefactor of nations ; and if such blessings 
are enjoyed without any grateful remembrance, history has con- 
descended to notice the more apparent luxuries of silk and 
sugar, which were transported into Italy from Greece and 
Egypt." (Gibbon, General consequences of the Crusades^ Vol. XL 
p, 289. Edit. 1813.) 

2 Hume. Edward V. 



SECT. I.] THIRD DISSERTATION. 13 

powder has, with all appearance of justice, been attri- 
buted/ *'From saltpetre and other ingredients," he says, 
" we are able to form a fire which will burn to any dis- 
tance." And again, alluding to its effects, '' a small por- 
tion of matter, about the size of the thumb, properly dis- 
posed, will make a tremendous sound and coruscation, by 
which cities and armies might be destroyed." And again, 
in the same work, is a passage which, though somewhat 
enigmatical, is supposed to divulge the secret of this prepa- 
ration. " Sed tamen salis petrae, lurii mone cap urbre, et 
sulphuris, et sic facies tonitrum si scias artificium." The 
anagram is convertible into carbonum ptilvere. Such are 
the claims of Roger Bacon to a discovery which soon 
changed the whole art of war. 

The works of Bacon most deserving perusal are the 
Opus Majlis, edited by Dr. Jebb in 17;33; and his Epis- 
tola de secretis Operibiis Artis et Naturae, et de mdlitatt 
Magiae. Paris, 1532. The former, addressed to Pope 
Clement IV., breathes sentiments which would do honour 
to the most refined periods of science, and in which many 
of the advantages likely to be derived from that mode of 
investigation insisted upon by his great successor Chan- 
cellor Bacon, are anticipated. 

Raymond Lully, Arnold of Villanova,- John de Rupe- 
scissa, and Isaac and John of Holland,^ were Alchemists 

* Watson's Chemical Essays, Vol. I. 

It has been by some imagined, that Roger Bacon invented the 
air-pump; but the idea rests upon very doubtful expressions. 
(Boerhaave, Instit. Prolegom,) 

^Raymond Lully was born in Majorca in 1236, and Villa- 
nova in Provence 1235. Their writings are as obscure as they 
are voluminous. 

^ " Sequuntur nunc Johannes et Isaacus Hollandus, pater et 
filius, (|ui (litfusissnno sermone rt magna eloquentia scripserunt, 
et si unum vel alterum arcanum cxceperis, pulchcnima cxperi- 



14 THIRD DISSERTATION. [sect. i. 

of the thirteenth, fourteenth, and early part of the fifteenth 
century. Their writings are extremely numerous ; and 
they each treat of the philosopher's stone, and other 
secrets of the occult science. 

Basil Valentine of Erfurt, who wrote towards the end of 
the fifteenth centurj, is deserving of more attention, and 
ranks among the first who introduced metallick preparations 
into medicine. In his Vurriis Trhimphalis Antimoniiy 
after setting forth the chemical preparations of that metal, 
he enumerates their medicinal effects. According to the 
notions of the age, he boasts of supernatural assistance ; 
and his work furnishes a good specimen of the controversial 
disputes between the chemical physicians and those of the 
school of Galen,-"the former being attached to active 
remedies, the latter to more simple and inert medicines. 
The Chariot of Antimony opens with the most pious 
exhortations to prayer and contemplation, to charity and 
benevolence. But the author, soon forgetting himself, 
breaks out in the following strain of virulent invective. 
"Ye wretched and pitiful medicasters, who, full of deceit, 
breathe out I know not what Thrasonick brags ;— infamous 
men, more mad than Bacchanalian fools ! who will neither 
learn, nor dirty your hands with coals ! you titular doctors, 

menta fecerunt de sanguine et urina humana, quae Helmontius 
postea et Boylaeus pro recentioribus inventis habuerunt." (Boer- 
baa ve.) 

^ It is probable that the word Antimony \vas first used by 
Basil Valentine. Tradition relates, that having thrown some of 
it to the hogs, after it had purged them heartily, they imme- 
diately fattened ; and, therefore, he imagined, that his fellow 
monks would be the better for a like dose, they having become 
lean by fasting and mortification. The experiment, however, 
failed, and they died 5 whence the medicine was called Anti- 
moine. 

He published several other works besides the CmiKS Triimi' 
phalis Antimonii. See Chalmer's Biograpk, Diet, 



sECT.i.) THIRD DISSERTATION, 15 

who write long scrolls of receipts ; you apothecaries, who 
with your decoctions fill pots no less than those in princes* 
courts, in which meat is boiled for the sustenance of some 
hundreds of men ; you, I say, who have hitherto been 
blind, suffer a colly rium to be poured into your eyes, and 
permit me to anoint them with balsam, that this ignorance 
may fall from your sight, and that you may behold truth as 
in a clear glass. But," says Basil Valentine, after a long 
exhortation in this strain, " I will put an end to my dis- 
course, lest my tears, which I can scarcely prevent con- 
tinually falling from my eyes, should blot my writing, and, 
whilst I deplore the blindness of the world, blemish the 
lamentation which I would publish to all men." 

Such is the trash in which these authors abound, and in 
which curious facts and ingenious speculations are often 
enveloped. 

Basil Valentine was succeeded by the more celebrated 
Paracelsus, a native of a village near Zurich in Switzer- 
land.' In this remaikable person, all the follies and ex- 
travagance of the Alchemists were united ;— he pretended 
to the discovery of the grand secret of the universal reme- 
dy ; and his writings, which are very numerous, overflow 
with the whims and oddities of the sect ; his zeal was more 
directed to the acquisition of popularity than to the ad- 
vancement of science ; his enthusiasm was ever misem- 
ployed ; and he sou[;ht the elevation of his own character 

' He assumed the formidable title of Phiiippus Aureolus Theo- 
phrastus Bomhastiis Paracelsus ab Hohenheim. 

" Hunc virum," says Boerhaave, "alii coluerunt pro Deo, imo 
locutus sum cum hominibus qui creduut enm non esse niortuum, 
sed vivum sedere in sepulchro pertaesum peccatorum et malo- 
rura hominum." The following is an illustrative anecdote of 
his impudence: '* Cum adsctnderet Calhedram physico-raedi- 
cam, sumsil vas aeneum cum iu^ne, immisit sulphur et nitrum, et 
simul Galenum, Avicennnm, et Arabes conjecit in ignem, 
dicenSj sic vos ardebitis in gelienn&." 



16 THIRD DISSERTATION, [shct. i. 

in the abuse and depreciation of his predecessors and con- 
temporaries. He terminated a life, stained with every 
vice, and deficient in every virtue, in the year 1541, at an 
obscure inn at Saltzbourg, in Bavaria. 

In the history of medicine, Paracelsus deserves more 
honourable mention ; for he enriched the Materia Me- 
dica with many powerful remedies, derived from the mine- 
ral world, among which several preparations of mercury 
deserve especial notice ; nor was he unacquainted with the 
virtues of opium, and other powerful drugs of vegetable 
origin. These he administered with a daring but often 
successful hand, and gained such celebrity, that, in 1527, 
he was promoted by the magistracy of Basle to the office 
of Professor of Physick. In this he expounded his own 
doctrines, asserting that that which was denied him from 
above had been granted by the infernal deities ; and that 
to them he was indebted for those great secrets of phy- 
sick and philosophy which he should divulge for the ad- 
vantage and salvation of his hearers. Paracelsus, how^ever, 
soon became weary of his situation, and terminated his 
professorial career, which was ill suited to his genius and 
inclinations, in the year 1528 ; he left Basle, and his sub- 
sequent life was one disgusting scene of dissolute irregula- 
rity. 

The last person whose name deserves to remain upon 
the chemical records of the sixteenth century is Van Hel- 
mont of Brussels, born in 1577',^ who, at an early age, made 
considerable progress in philosophical studies. As a phy- 
sician, he adopted the doctrines of the chemical school, 
and rejected those of Aiisiotie and Galen; he effected 
cures so numerous and surprising, that he was accused by 

^ The year 1538, given in Moreri. Dictionnaire Hist is obvi- 
ously incorrect, *'Arjno 1594, qui erat niihi decimus se^timus," 
&c. (Van Helmont, opera omnia, 1707. Studia Authoris.) 



iicT. I.] THIRD DISSERTATION. 17 

the inquisition of employing supernatural means, which in- 
duced him to retire into Holland. The writings of Van 
Helmont are chiefly upon medical subjects ; those con- 
nected with chemistry contain some curious speculations 
respecting aeriform fluids, which he calls gases, a term 
now in common use. He also speaks of a subtile invisible 
agent, called Bias, which, he says, is an etherial emanation 
from the heavenly bodies. '* Winds are air agitated by 
the Bias of the stars. "^ 

The doctrine of the Four Elements, as established by 
the ancient philosophers, underwent several alterations in 
the hands of the chemists of the sixteenth century. The 
former regarded Earth, Water, Air, and Fire, as the uni- 
versal rudiments of all matter, and assigned to each its 
particular station in the universe. Earth tended towards 
the centre, water to the surface of the globe ; air occupied 
a middle station between water and 6re ; which last was 
considered as the most rare, subtile, and active of all 
things ; it was supposed to constitute the heavenly bodies, 
and to confer life and action upon the other principles, to 
various combinations of which the diSerent productions of 
naiure were referred. 

Basil Valentine, Paracelsus, and Van Helmont, speak of 
Salt, Sulphur, and Mercury, as the elementary principles 
of bodies ; but (he passages in their works referring to this 
hypothesis, are too dark and absurd to merit quotation ; it 
was, however, adopted by several of their contemporaries 
and successors. 

* " Nescivit inquam schola Galenica hactenus tliflerentiam 
inter gas ventosum, quod mere aer est, id est, ventus per siderum 
bias (!ommotu3, gas pingue, gas siecum, quod sublimatum dicilur, 
gas fuliginosum sive enderaicum, et gas silvestre sive incuerci- 
bile, quod in corpus nou cogi potest visibile." {Opa\ om. 
p. 399. 



18 THIRD DISSERTATION* [sect, i. 

During* the sixteenth century, some progress was made 
in the elucidation of the chemical arts, especially of Metal- 
hirgy, upon which subject the works of Agricola,^ and of 
Lazarus Erckern, merit particular notice. The former has 
detailed, at considerable length, the various operations em- 
ployed in mining, and his descriptions are at once correct 
and elegant ; but his attempts at theory are deeply tinctured 
with the prevailing follies of the age. Agricola, who died 
at Chemnitz in 1555, was succeeded by Erckern, superin- 
tendant-general of the German mines ; " he is an experi- 
enced, candid, and honest writer, relates nothing but what 
he had himself seen, without a word of theory or reasoning, 
and every where speaks as if he were sitting before the 
furnace and relating what passed."^ 

After wading through the thick fog of alchemical specu- 
lation, which envelopes the writers of this period, it is a 
relief to meet with one whose details are thus intelligible, 
and who adheres to matter of fact. 

The periods we have now considered, teemed with search- 
ers for the philosophers stone, — the elixir of life, — and the 
universal medicine. Of these such have hitherto only been 
noticed, as conduced, by their experiments and discoveries, 
to the progress of chemical science. 

* The mineralogical works of Agricola display very minute 
information upon the most important parts of his subject. They 
are, 1. De ortu el causis snbkrraneorum. 2. De natura eormn quae 
effiuunt ex terra. 3. De natura Fossilium, 5. De medicatis fon- 
tibus. 6. De suhterrancis animantihus. 7. De veteribus et novis 
metallis. 8. De re mctallica. This last has passed through seve- 
ral editions, and is an excellent compendium of what was then 
known upon the theory and practice of the miners art, and of 
the working of metals. 

^ ** Liber ejus (Lazer. Erckern), in folio, est editus lingua Teu- 
tonica, pollicem crassus et iterum recusus est in Germana, in 4to. 
Est auctor in hac parte optimus." (Boerhaave.) 



ncr. I.] THIRD DISSERTATION. 19 

The records of the fifteenth and sixteenth centuries pre- 
sent a motley group of these adventurers solely devoted to 
the occult art of transmutation. Some were open impos- 
tors ; others deluded believers ; but their respective histo- 
ries are, in general, so similar, that an account of one will 
suffice :' Bernard Trevisan, who was born at Paris early in 
the fifteenth century, and who suffered severely under this 
intellectual epidemick, may be cited for the purpose. He 
commenced his career with the unsuccessful repetition of 
certain processes of transmutation described by Rhazes, in 
which he expended eight hundred crowns. The perusal 
of Geber's treatise on the perfection of the metals rekin- 
dled his hopes, and, after wasting two thousand crowns upon 
apparatus and materials, this experiment proved as fruitless 
as the former. The writings of Ruspescissa, Archelaus, 
and Sacrobosca, shortly afterwards engaged his notice ; 
and, to ensure success, he associated himself with a monk, 
and performed a variety of silly but laborious experiments, 
at the expense of more than a thousand crowns. He sub- 
mitted the same portion of spirit of wine to three hundred 

* Among the English alchemists, we may enumerate George 
Ripley, who, in 1471, wrote the Compound of Alchcmie^ dedicated 
to Edward IV. ; and the celebrated Ellas AsJimole, who called 
himself Mercuriophibts Anglicus, and who published and edited 
many treatises on alchemy. He founded the Ashmolean Muse- 
um at Oxford in 1679. The reader, who maj wish to amuse 
himself with the nonsense of our own alchemists, is referred to 
the ThcatrumChemicum Britannicum, containing severall pocticaU 
pieces of our famous English philosophers who have written the Her- 
metique mysteries in their owne anticnt language, Bj/ Elias Ash- 
mole, Esq. Qui est Mercuriophilus Anglicus ; and to the celebrated 
alchemical work Philalethes. 

The following act of parliament, which Lord Coke calls the 
shortest he ever met with, was passed in the fifth year of Henry 
IV. : " None from henceforth shall use to multiply o;oI(l or silver, 
or use the craft of multi[)lications, and if any the same do, he shall 
incur the pain of felony." f Watson's Chemical Essays.) 



20 THIRD DISSERTATION. [sect. i. 

distillations, and was engaged during a period of twelve 
years, in a series of fruitless and unmeaning operations upon 
alum, common salt, and copperas. At length he quitted his 
native country for Italy ; thence he proceeded to Spain 
and Turkey, in search of the adepts of the art, from whom 
he hoped to acquire the secret, and reimburse himself. 
Thus having squandered the scanty remains of his broken 
fortune, and reduced nearly to beggary, he retired to the 
isle of Rhodes, where be entered the service of Arnold of 
Villa Nova, from whom he states that he obtained that 
which he so long searched for. So true is that definition 
of Alchemy, which describes it as an art without principle, 
which begins in falsehood, proceeds in labour, and ends in 
beggary. 

Entering upon the seventeenth century, the historian of 
Experimental Science must ever pause to pay a tribute of 
gi-atitude and respect to the celebrated Francis Bacon ; a 
man whose faults as a statesman have been eclipsed to the 
eyes of posterity, by the brilliancy and excellence of bis 
philosophical character. 

It may commonly be observed, that those who are gifted 
by nature with superiour genius or uncommon capacity, — 
who are destined to reach the meridian of science, or to at- 
tain exalted stations in the learned professions, have exhibit- 
ed early symptoms of future greatness ; either indefafiga- 
ble industry, or extraordinary sagacity, or ardent enthusi- 
asm, have marked their entrance into the affairs of life. At 
the age of sixteen, Bacon was distinguished at Cambridge ; 
and, very shortly afterwards, struck with the frivolous 
subtilty of the tenets of Aristotle, he appears to have turn- 
ed his mind into that channel, which led on to future emi- 
nence. The solid foundation of his scientifick character is 
the Instauration of the Sciences, It opens with a general 
and philosophical survey of the subject ; whence he pro- 



sicT. 1.] THIRD DISSERTATION. 21 

ceeds to infer the futility of the ancient philosophical sys- 
tems, and to point out Induction, from sober and severe ex- 
periments, as the only road to truth. Pursue this, he says, 
and we shall obtain new powers over nature ; we shall per- 
form works as much greater than were supposed practica- 
ble by natural magick, as the real actions of a Caesar surpas- 
sed the fictitious ones of a hero of romance. 

Speculative philosophy he likens to the lark, who brings 
no returns from his elevated flights ; experimental philoso- 
phy to the falcon, who soars as high, and returns the pos- 
sessor of his prey. 

Illustrations of the new method of philosophizing, and 
the mode of arranging results, conclude this admirable and 
unrivalled performance. 

To do justice to this work, we must, for a moment, forget 
the present healthy and vigorous constitution of science, 
and view it deformed and sickly in the reign of Elizabeth. 
We shall then not be surprised at the irrelative observa- 
tions and credulous details, which occasionally blemish this 
masterly production of the human mind. 

But the history of Lord Bacon furnishes other materials 
for reflection. Upon the accession of James I., he became 
successively possessed of the highest honours of the law, 
and acquired great celebrity as a publick speaker and a man 
of business ; yet, amidst the harassing duties of his labori- 
ous avocations, he still found time to cultivate and adorn the 
paths of science, the pursuit of which furnished employ- 
ment for his scanty leisure, and relaxation in his professional 
toils ; and, when ultimately disgraced, '* his genius, yei un- 
broken, supported itself amidst involve^ circumstances and 
a depressed spirit, and shone out in literary productions." 
Nor should the munificence of his royal master remain nn- 
mentioned, who, after remitting his fine, and releasing him 
from his prison in the Tower, conferred on him a large pen- 



22 THIRD DISSERTATION, [sbci«. i. 

sion, and used every expedient to alleviate the burden of 
his age, and to blunt the poignancy of his sufferings. 

After the death of Lord Bacon, which happened in 
April 1626, in the 66th year of his age, the records of sci- 
ence began to assume a brighter aspect ; and we discern 
true knowledge emerging from the dungeons of scholastick 
controversy, and shaking off the shackles of polemical 
learning. 

The philosophers by fire, as the Chemists were empha- 
tically termed, no longer exclusively engaged in seeking for 
the elixir of life, and the stone of transmutation, began to 
direct their endeavours towards more attainable and useful 
objects. They availed themselves of the accumulated facts 
collected by the misguided zeal and barren labours of their 
predecessors, and combined these useless and unseemly 
materials into the foundations of a beautiful and useful de- 
partment of knowledge ; but their progress was slow, and 
not unfrequently interrupted by relapse into the follies of 
Alchemy. 

Glauber of Amsterdam,* and in this country, the Honoura- 
ble Robert Boyle, are characteristick writers of the middle 
of the seventeenth century. The former has detailed ma- 
ny curious and interesting facts respecting neutral salts, 
acids, and animal and vegetable substances ; but his descrip- 
tions are darkened by the language of the adepts, and valu- 
able truths are disguised by being blended with the unin- 
telligible jargon of the black art. 

The perusal of Glauber's chemical works leads to some 
surprise at the multitude of facts with which he was ac- 
quainted, and, among them, we meet with discoveries which 
have been considered of modern date. He particularly 

* A collection of Glauber's works, in Latin, was published at 
Frankfort, in 1658, in 8vo, and in 1659 in 4to. An English 
translation was published at London, in 1689, by C. Pack. 



SECT. 1.] THIRD DISSERTATION. 23 

describes the production of vinegar during the destructive 
distillation of wood. {Miraculiim Mundij p. 1.) The 
following may be selected from among many similar pas- 
sages in his writings, as exhibiting the active and original 
turn of mind of this keen and curious inquirer, and as con- 
taining the germ of many truths which have been more ful- 
ly developed in our own time. 

" But what other things the said juice of wood is able to 
effect, we cannot here declare, by reason of our intended 
brevity ; yet this I will add, that, if this acid spirit be rec- 
tified, it may be used in the preparation of good medicines ; 
in mechanick arts ; in the making of many fair colours from 
the extraction of metals, minerals, and stones ; and for all 
things for which common vinegar is used ; yea, far more 
commodiously, because it much cxceedeth common wine 
and beer vinegar in sharpness.'' 

He also mentions the tar produced in the same process, 
which he recommends as efficacious in preserving wood that 
is exposed to weather, and speaks of it, when mixed with 
ashes, as a profitable and quickly acting manure. He fur- 
ther points out the method of concentrating the vinegar of 
wood by exposure to cold, " which freezes the phlegm only, 
but the sharp spirit is not turned into ice, but remaineth in 
the middle of the hogshead, so sharp that it corrodeth me- 
tals like aqua-fortis. If hop-poles be dipped in the oil, it 
not only preserves them, but fattens the plant ; and as in* 
sects abbor these hot oils, if they be applied to the bark of 
fruit trees, it will defend them from spiders, ants, canker- 
worms, and other insects ; by this means also, rats and 
mice may be prevented from creeping up hovel posts, and 
devouring the grain." Glauber details a number of experi- 
ments relating to the action of this vinegar of wood, on 
limestone, and notices the use of its compounds ; and that 
he was accurately acquainted with its superiour acidity, ap- 



24 THIRD DISSERTATION. [iEci. i. 

pears from the following quotation : '' It is said that Han- 
nibal made a passage through the Alps for himself and his 
army, softening the rocks bv the benefit of vinegar. What 
vinegar that was, hisioiies do not mention. Perhaps it was 
the vinegar of wine ; but if he had had the vinegar of wood, 
he mi2:ht sooner have attained his desire." 

These shrewd remarks and useful observations are thicklj 
scattered through the verbose pages of Glauber. He enrich- 
ed the laboratory with new agents, and into medicine he in- 
troduced several new and useful remedies. Upon the arts 
he bestowed many improvements, and was among the 6rst 
who seriously endeavoured to benefit agriculture by the me- 
dium of experimental chemistry. 

Bo\ie^ has left voluminous proofs of his attachment to 
scientitick pursuits, but his experiments are too miscellane- 
ous and desultory to have afforded either brilliant or useful 
results ; his reasoning is seldom satisfactory ; and a broad 
vein of prolixity traverses his philosophical works. He 
was too fond of mechanical philosophy to shine in Chemis- 
trVj ^nd gave too much time and attention to theological and 
metaphvsical controversy to attain any excellence in either 
of the former studies. He who would do justice to Boyle's 
scientific character, must found il rather upon the indirect 
benefits which he conferred, than upon any immediate aid 
which he lent to science. He exhibited a variety of ex- 
periments in publick, which kindled the zeal of others more 
capable than himsell*. He was always open to conviction : 
and courted opposition and controversy, upon the principle 
that *ruth is often elicited by the conflict of opinions. His 

^ Boyle was born in January 1627, at Lismore. in the {province 
of Munster, in Ireland. He was educated at Eton, and rfter- 
wards travelled in Italy, Switzerland, and France, and returned 
to Enei^nd in 16-J4. In 1668 he took uo his resuitr'ncp ii) Lon- 
don ; at' i in 1680 was elected President of the Royal Society. 
He died on the 30th of December 1691; aged 65. 



fiicT. I.] THIRD DISSERTATION. 25 

disposition was ever aaiiable, mild, and generous, and he was 
at once the patron of learning and of virtue. 

The merit of bringing Hooke^ before the publick, and of 
pointing out to him the road to eminence, is chiefly due to 
Mr. Boyle, who, in the troublesome and bigoUed periods 
of the commonwealth and protector^ihip, associated himself 
with a few philosophical friends at Oxford, for the purpose 
of promoting experimental inquiry. Hooke, who enjoyed 
the advantage of having been educated at Westminster 
school, under Dr. Busby, was introduced in the year 1655 
to this select society, where his original and inventive ge- 
nius was soon discerned and called into action. Boyle en- 
gaged him as his operator and assistant, and his talents were 
turned with great success, to the invention and improve- 
ment of philosophical instruments, and to many important 
subjects connected with the mechanical arts. 

It was about this period that the physical properties of 
the atmosphere began to attract notice, and that the favour- 
ite scholaslick notion of Nature's abhorrence of a vacuum 
was called into question. Galileo was, perhaps, the first 

* Sir Godfrey Copley, in a letter written about the time of 
Hooke's death, says, *' Dr. Hooke is very crazy ; much concerned 
for fear he should outlive his estate. He hath starved one old 
woman already, and, I believe, he will endanger himself to 
save sixpence for any thing he wants." In another, written a 
few ^veeks after his death, Sir Godfrey says, " I wonder old Dr. 
Hooke did not choose rather to leave his 12,000/. to continue 
what he had promoted and studied all the days of his life, — I 
mean mathematical experiments, than to liave it ^o to those 
whom lie never saw nor cared for. It is rare that virtuosos die 
rich, and it is pity they should, if they were like him/' {Dr. 
DucarrePs MSS. quoted in Bioii'. Diet.) Hooke sometimes de- 
clared, that he intended to dispose of his estate for the advance- 
ment of natural knowledge, and to promote the ends for which 
the Royal Society was instituted ; to build a handsome edifice for 
the Society's use, with a library, laboratory, and repository, and 
to endow a professorship. {Life hy Waller,) 



£6 THIRD DISSERTATION. [srct. i. 

who broke this spell of Aristotelian philosophy ; and in 
the year 1644, the grand discovery of atmospherick pres- 
sure, and its variatipn, was announced by Torricelli, the 
celebrated inventor of the barometer/ The idea of con- 
structing a machine for the purpose of rarefying air, first 
occurred to Otto Guericke, who, after many fruitless 
attempts, succeeded by means of a sucking pump, in with- 
drawing a considerable portion of air from the interiour of 
a copper ball. With this awkward and imperfect air- 
pump, he performed several notable experiments. One 
of these is often exhibited at the present day. It consists 
in exhausting a hollow brass globe, composed of two hemi- 
spheres, closely fitted to each other. When a portion of 
the interiour air is removed, the pressure of the exteriour 
atmosphere is such, as to resist considerable force applied 
to separate the hemispheres. This is called the Magde- 
burgh experiment, and was first publickly exhibited in the 
year 1654 before the deputies of the empire, and foreign 
ministers assembled at the diet of Ratisbon. This original 
air-pump, invented by the Burgomaster of Magdeburgh, 
was greatly improved by Hooke, who, in conjunction with 
Boyle, performed by its means a variety of new and im- 
portant experiments, illustrative of the mechanical proper- 
ties of the atmosphere, which, at a subsequent period, 

^ The Peripateticks maintained, that the creation of a vacuum 
was impossible, even to supernatural power. This dogma was 
first shaken by a circumstance which happened to some workmen 
employed by the Grand Duke of Tuscany. Having sunk a deep 
well, they endeavoured to bring the water to the surface by a 
common sucking pump, but found, to their surprise, that they 
could only make it ascend to the height of about 30 feet. Ga- 
lileo, whose talents had gained him great celebrity and respect^ 
was consulted in this emergency. His answer was, that, although 
nature does dislike a vacuum, there is a certain limit to her an- 
tipathy, equivalent to the pressure of a column of water eighteen 
palms high. 



fiECT.i] THIRD DISSERTATION. 27 

tended considerably to the progress of pneumatick chemis- 
try. 

The works of Hooke, chiefly interesting to the chemist, 
are his Micrographia and LampaSj the former published 
in 1664, the latter in 1677. They contain anticipations of 
many of the subsequent changes and improvements of 
chemical theory, which will be noticed in a future page of 
this history. 

Both the private and publick character of Dr. Hooke 
exhibit many faults, and are stained with many blemishes. 
His temper was peevish, reserved, and mistrustful ; and he 
wanted that candour and dignity of mind which should 
raise the philosopher above the level of ordinary men. He 
was born at Freshwater, in the Isle of Wight, in 1635, and 
died in London in the year 1702. 

Immediately after the Restoration, the gentlemen who 
formed the Philosophical Society at Oxford adjourned to 
London, where they held their meetings in Gresfaam Col- 
lege, and considerably extended the number of their mem- 
bers. The King, who himself loved science, countenanced 
and patronized their proceedings; and, on the 15th of 
July 1662, granted a royal charter, constituting them a 
body corporate, under the name of The Royal Society of 
London, for promoting Natural Knowledge. In the 
year 1665 was published the first number of the Philo- 
sophical Transactions, of which work, justly regarded as 
the standard of English science, a volume has been pub- 
lished annually since the year 1762. 

This laudable and rare example of Charles the Second 
was followed by Lewis the Fourteenth of France ; and in 
the year 1666 the Royal Academy of Sciences was insti- 
tuted at Paris, under the immediate protection of that 
monarch. Neither was the patronage cold, nor the ho- 
nours empty, which were bestowed by Lewis on the fol- 



28 THIRD DISSERTATION, [sect. i. 

lowers of science. Salaries he conferred upon scientifick 
bodies, and pensions upon learned men, " a generosity," 
says Hume, "which does great honour to his memory, and 
in the eyes of all the ingenious part of mankind will be 
esteemed an atonement for many of the errours of his reign. 
We may be surprised," continues the historian, " that this 
example should not be more followed by Princes, since it 
is certain that bounty so extensive, so beneficial, and so 
much celebrated, cost not this monarch so great a sum as 
is often conferred upon one useless overgrown favourite or 
courtier." Happily for the scientifick character of Britain, 
the genius, talents, and exertions of individuals have ever 
been sufficient to counterbalance such advantages ; and 
thus nurtured and protected, the growth of science has not 
been less rapid or vigorous than where she has enjoyed the 
sunshine of royal favour. 

With the great and unrivalled name of Newton, we close 
the records of the seventeenth century. To him Chemis- 
try is indebted for the first correct views respecting the 
nature of combination ; a subject which had little engaged 
the attention of the more sensible experimentalists of the 
preceding periods, and which was formerly attributed to 
the occult qualities of the Aristotelians, and afterwards to 
the mechanical forms of the particles of bodies.^ 

Chemical affinity was referred by Newton to the diffe- 
rent attractive powers of the different kinds of matter in 
regard to each other. Salt of tartar becomes moist by 
exposure to air, because that salt attracts the humidity of 
the atmosphere. Muriatick acid unites with salt of tartar 
by virtue of their respective attractions ; but when oil of 

* We shall again have occasion to refer to certain chemical 
opinions of Newton. In the present instance, reference is made 
to the thirty-first query annexed to the Third Book of Opticks, 
(Newton, Opera Omnia^ 4t0j Lond, 1782.) 



sKCT.i.] THIRD DISSERTATION. 29 

vitriol is poured upon this compound, the former acid is 
displaced by the superiour attraction of the latter. Silver 
dissolved in aqua-fortis is separated from that menstruum 
by the superiour attraction of quicksilver; in like manner 
copper separates quicksilver ; and iron, copper. Refer- 
ring to these and other similar instances, *' does not this" 
says he " argue, that the acid particles of the aqua-fortis ' 
are attracted more strongly by iron than by copper, by 
copper than by quicksilver, and by quicksilver than by 
silver ?" Such are the simple but clear, and, in most in- 
stances, correct suggestions, relating to the subject of at- 
traction, which Chemistry owes to the great luminary of 
Mechanical Philosophy. 

In tracing the history of Chemistry from early times, 
through the dark ages, to the beginning of the last century, 
I have noticed only such authors as conduced by the 
weight or novelty of their writings, the importance of their 
discoveries, or the example of their zeal, to the more 
immediate progress and elucidation of this department of 
philosophy. The annals of a period so extensive must 
necessarily record a host of experimentalists, to whose 
researches it would upon the one hand be impossible to do 
justice ; and whose names, on the other, it would be use- 
less to repeat. It may however be remarked, that alem- 
bicks, and other complex distillatory apparatus, were em- 
ployed by the alchemical physicians who flourished be- 
tween the ninth and thirteenth centuries. Mesne mentions 
the distillation of rose-water, and the production of spirit 
of wine is noticed by Raymond Lully. At this time, too, 
furnaces of peculiar construction, and a variety of complex 
apparatus and accoutrements, were introduced into the 
laboratory. 

During the fifteenth and sixteenth centuries, Alchemy 
was at its acme, and many were the unwary and avaricious 



30 THIRD DISSERTATION. [sect. i. 

who were entrapped by the golden prospects and plausible 
mysiicism of the art. Among them was that admirable 
artist Mazzuoli of Parma, better known under the name of 
Parmagiano. 

Curious discoveries and useful inventions multiplied ra- 
pidly during the seventeenth century. Kunciiel, in Saxo- 
ny, successfully promoted the Chemistry of the Arts. In 
1669, Brandt of Berlin discovered Phosphorus, and about 
the same time Homberg accidentally produced a sponta- 
neously inflammable compound, which he called Pyropho- 
rus. In 16T4 the elder Lemery acquired great and de- 
served fame at Paris as a chemical lecturer. He was the 
first who threw aside the affected and pompous diction 
habitually indulged in by his predecessors and contempo- 
raries, and adopted a simple and perspicuous style, which 
at once tended to the ready diffusion of his subject, and 
to its permanent popularity. When he published his 
course, " it sold'* says Fontenelle " like a novel or a 
satire." 

The establishment of literary and scientifick societies 
during this age was another grand step towards the promo- 
tion of knowledge, and the period was particularly propi- 
tious to their progress. Bacon, Galileo, and Kepler, had 
opened that road to truth which was so eagerly and suc- 
cessfully pursued by Boyle, Hooke, and Mayow, in this 
country, and in which the miraculous mind of Newton 
displayed its brilliant powers. In Germany, Beccher and 
Stahl are entitled to particular mention. The suggestions 
of the former, who was a man of an acute and inquisitive 
turn of mind, led the latter into that train of speculation 
which terminated in producing the Phlogistick Theory, 
and which will presently be more particularly considered. 
Homberg, Geoffroy, and the two Lemerys, were zealous 
followers of experimental chemistry in France, at the 



SECT. II.] THIRD DISSERTATION. 31 

establishment of the Rojal Academy of Sciences. In 
short, the independent zeal and healthy activity in scien- 
tifick pursuit, which has since marked its progress in 
Europe, became manifest early in the seventeenth centu- 
ry ; and the causes I have attempted to unfold contributed 
to the splendour which it began to acquire about the end 
of that iixijioitaut era in the general history of the world. 
The clouds of ignorance and errour quickly dispersed 
before (his happj^ dawn of true knowledge ; and science, 
no longer enveloped in scholastick mystery and absurd 
speculation, began to display those inherent charms, which 
gained her the courtship and admiration of every liberal 
and cultivated mind, and which laid the foundation of that 
extended dominion which she acquired in the succeeding 
age.' 



SECTION IJ. 

STATE OF CHEMISTRY AT THE OPENING OF THE EIGHTEENTH CEN- 
TURY.-— OPINIONS OF BECCHER AND STAHL RESPECTING THE PHE- 
NOMENA OF COMBUSTION, COMPARED WITH THE VIEWS OF REY AND 

MATOW. — PNEUMATICK CHExMISTRY OF HAILES AND BOERHAAVE. 

INVENTION OF THE THERMOMETER. 

The history of the progress of Chemistry during the 
seventeenth century presents many active and able inqui- 
rers, whose researches tended to develope new properties 
and combinations of bodies; but their attempts at theory 

' Those who are desirous of consulting the alchemical autliors, 
and of becoming particularly acquainted ^Yith the titles of their 
voluminous productions, will find a curious body of information 
on these subjects in the Histoirc dc la Philosophic Hcrmctiquc, Pa- 
ris, 1712.— Gobet's Ancicns Mincralo^istcs, published at Paris in 
1779, gives some details of the early progress of 3IineraIogicaI 
Chemistry in France. 



32 THIRD DISSERTATION. [skct. h 

and generalization were, with few exceptions, absurd and 
abortive. They consisted in wild hypothesis and vague 
speculation, and were founded, not upon the sober and 
steady basis of truth, but upon the unreal and tottering 
visions of the imagination. The spirit of Lord Bacon was 
slow in animating experimental philosophy, until Newton 
rose to surprise and illumine the world. It then assumed 
a new and cheerful aspect, and quick was its growth, and 
illustrious its progress, under the invigorating influence of 
that sun of science. 

Although Chemistry does not lie under the same weighty 
obligations to Newton as mechanical philosophy, he con- 
ferred upon it a great and lasting benefit, by the disclosure 
of those clear and simple views which have already been 
alluded to.' The important deductions, too, which flow in 

^ The following passages, in addition to the previous observa- 
tions in the text, wili be sufficient in illustration of Newton's 
views of Elective Attractions, 

" Have not the small particles of bodies certain powers, vir- 
tues, or forces, by which they act at a distance, not only upon 
the rays of light, for reflecting, refracting, and inflecting them, 
but also upon one another, for producing a great part of the 
phenomena of nature ? for, it is well knowq, that bodies act one 
upon another by the attractions of gravity, magnetism, and elec- 
tricity ; and these instances show tbe tenor and course of nature, 
and make it not improbable that there may be more attractive 
powers than these. For nature is very consonant and conform- 
able to herself. How these attractions may be performed I do 
not here consider; what I call attraction may be performed by 
impulse, or by some other means unknown to me. I use that 
word here to signify only, in general, any force by which bodies 
tend towards one another, whatsoever be the cause. For we 
must learn from the phenomena of nature, what bodies attract 
one another, and what are the laws and properties of the attrac- 
tion, before we inquire the cause by which the attraction is 
performed. The attraction of gravity, magnetism, and elec- 
tricity, reach to very sensible distances, and so have been ob- 
served by vulgar eyes, and there may be others which reach to 
so small distances as hitherto escape observation, and perhaps 
electrical attraction may reach to such small distances even 



sECT.n.] THIRD DISSERTATION. 33 

easy perspicuity from his experimental researches, soon 
became general models of imitation ; and the new style 
which we discern in the philosophical authors of the early 
part of the eighteenth century throughout Europe, may, in 
a great measure, be referred to the lofty example before us. 
No sooner was the spell of Alchemy broken, than the 
phenomena of combustion began to attract the notice of the 

without being excited by friction. For, when salt of tartar 
runs per deliquium, is not this done by an attraction between the 
particles of the salt of tartar and the particles of the water which 
float in the air in the form of vapours ? And why does not com- 
mon salt, or saltpetre, or vitriol, run per deliquium, but for want 
of such an attraction ? Or why does not salt of tartar draw more 
water out of the air than in a certain proportion to its quantity, 
but for want of an attractive force after it is satiated with water ? 
And whence is it but from this attractive power that water, 
which alone distils with a gentle and lukewarm heat, will not 
distil from salt of tartar, without a great heat ? And is it not 
from the like attractive power, between the particles of oil of 
vitriol and the particles of water, that oil of vitriol draws to it 
a good quantity of water out of the air ; and, after it is satiated, 
draws no more, and in distillation lets go the water very diffi- 
cultly ? And when the water and oil of vitriol, poured succes- 
sively into the same vessel, grow very hot in the mixing, does 
not this argue a great motion in the parts of the liquors ? And 
does not this motion argue that the parts of the two liquors, in 
mixing, coalesce with violence, and, by consequence, rush to- 
wards one another with an accelerated motion? And when 
aqua-fortis, or spirit of vitriol, poured upon filings of iron, dis- 
solves the filings with a great heat and ebullilion, is not this 
heat and ebullition effected by a violent motion of the parts?" 
&c. " When spirit of vitriol, poured upon common salt or salt- 
petre, makes an ebullition with the salt, and unites with it, and, 
in distillation, the spirit of the common salt or saltpetre comes 
over much easier than it would do before, and the acid part of 
the spirit of vitriol stays behind; — does not this argue that the 
fixed alcaly of the salt attracts the acid spirit of the vitriol, more 
strongly than its own spirit; and, not being able to hold ihem 
both, lets go its own ?"^ — Newton's Ontichs, Opera omnia, llo, 
Lond. 17r>2. 



34 THIRD DISSERTATIOIN. [sect. n. 

early chemical theorists. The influence of the air upon 
this process had been long observed, and many of the 
changes suffered bj the combustible, had been examined 
with a surprising degree of acuteness and precision ; for 
fire was almost the onlj agent employed at that period to 
effect combination and decomposition. These inquiries 
constitute a prominent feature in the history of Chemistry. 
It may therefore be requisite to pursue them with a minute 
attention, which may at first appear tedious, but which will 
gain in importance and interest as they proceed. 

The first speculations in theoretical Chemistry deserv- 
ing attention, are those of John Joachim Beccher of Spires, 
who died in England in 1685. He gained considerable 
celebrity at Vienna and Haerlem, for improvements in arts 
and manufactures, but was induced to retire to this country, 
in consequence of the jealousy of rivals, and the neglect of 
those upon whom he had conferred benefits. His works 
abound in shrewd and witty remarks, and in deep and curi- 
ous reasoning, — in frivolous subtilty, and in weighty and 
sensible observations. His hypothesis respecting the ori- 
gin of the varieties of matter, from the mutual agencies 
and combinations of a few elementary principles, though 
unnecessarily blended with scriptural history, are charac- 
terized by considerable brilliancy of thought and originality 
of invention. They are detailed at great length in his 
Physica Siibterraneay which treats on the original creation 
of matter, and the transition and interchange of elements. 
The Instihdiones Chemicae, or QSdipiis Chemlciis, of this 
author, is another curious production, containing the history 
of the chemical elements, and describing the leading opera- 
tions of the laboratory. Earth was the favourite element 
of this philosopher, of which he supposed three varieties to 
exist, namely, a vitrifiable, a metallick, and an inflammable 



sicr. IT.] THIRD DISSERTATION. 35 

earth. Of these the various productions of nature were 
formed.^ 

But the most celebrated chemical theorist of the latter 
part of the seventeenth century is Ernest Stahl, born at 
Anspach in Franconia, in 1660. He adopted many of the 
opinions of Beccher respecting the cause of inflammability, 
and upon these foundations reared the celebrated System 
of Phlogiston, according to which, inflammability is sup- 
posed to depend upon the presence of a highly subtile and 
elastick matter, which, at certain temperatures, is thrown 
into violent motion, and appears under the form of flame or 
fire. Combustion is the separation of this principle, and 
bodies contain it in various proportions. Charcoal, for in- 
stance, when burned, leaves scarcely any residuum, and is, 
therefore, nearly pure phlogiston. Antimony, when burn- 

^ Beccher wrote voluminously upon a great variety of subjects. 
His principal chemical works are as follows. 

1. Oedipus Ckeinicus. 2. Metallurgia, de generatione, rejitia- 
tione, et perfectione Metallonon, 3. Physica Suhterranea, and its 
various appendices. 4. Parnassus Medicinalis Ilhistratus, 5. 
Laboratorium Poriahile, 6. Ckymischer Rosen garten. 

Beccher's Oedipus is dedicated to Francis Sylvius Deleboe, 
who, in 1658, was elected the first Professor of Medicine in the 
University of Leyden. He was a man of an acute mind, as 
appears from his various essays and tracts, more especially from 
his Praxcos Med. Idea Nova. He died at Leydon in 1672. 
" Utilissimura profecto munus subiisti, quo tui auditores non 
verba sed corpora, non chymerasticos terminos, verum ipsas 
reales enchyrises, non inanes deuique et iramateriales facultates, 
sed a te demonstrati, effectus causas practicas audiunt, vident, 
tangunt" Beccher every where compliments him as a man 
not of words, but of deeds; as a philosopher, who eminently 
sought to render science popular and intelligible to all capaci- 
ties. 

The language of Beccher's Physica SuhtciTanca is sufficiently 
inelegant and incorrect. *' Excuso Lalinitalan in hoc opere," 
says he, ''quam harbaram esse fateor, ob materiem et ob scrip- 
tionem, in specie scriptionis modum: ex ore enim dictantis 
totum opus conceptum est. Sic rebus attenlus, verba neglexi." 
This is at once an example and apoloiry. 



36 THIKD DISSERTATION, [sect. h. 

ed, affords a large proportion of earthy matter. If this 
earth be heated with charcoal, or other matter abounding 
in phlogiston, antimony is regenerated ; this metal, there- 
fore, is a compound of earth and phlogiston. 

If sulphurick acid, which is not inflammable, be distilled 
with oil of turpentine, which is extremely so ; or, in other 
words, if phlogiston be added to sulphurick acid, sulphur 
is obtained. Sulphur, therefore, is a compound body, con- 
sisting of sulphurick acid and phlogiston. If sulphur and 
common soda be fused together, a brown compound is ob- 
tained, formerly called liver of sulphur, and the same pro- 
duct results when charcoal is heated with Glauber's salt, 
which consists of soda combined with sulphurick acid. 
Such was Stahl's explanation of the phenomena of com- 
bustion, and such the apparently plausible experimental 
proofs upon which it was founded.' 

In Germany and in France, the phlogistick doctrine was 
received with that thoughtless and eager enthusiasm which 
suffers the blaze of novelty to eclipse the steady light of 
truth, and which is rather captivated by plausible exteriour 
than by internal excellence. Even in this country the 
experiments of Boyle and of Hooke, if not forgotten, were 
over-looked, and hypothesis for a time gained the ascen- 

* Stahl's doctrines are very ably set forth in his Three Hun- 
dred Experiments^ published at Berlin in 1731 ; and in bis Funda- 
menta Chemiae, Nuremberg, 1723 and 1732. He observed the 
necessity of air to combustion, and considered flame or fire as 
resulting from its violent etherial agitations. Stahl is continually 
urging circumspection in hypotheses, yet preconceived opinions 
are always leading him to erroneous conclusions, as the following 
passages amply prove. "Aer ignis est anima. hinc, sine acre 
nihil potest accendi vel inflaramari." — Aer in motum excitatus, 
sen ventus artiflcialis, vel etiam naturalis, mirum excitat motum 
aetberis, seu flammam ; hinc ad ignem fusorium, et vitrificatorium, 
promovendum, follibus opus est ; imo gradus et vehementia ignis 
dependet multum ex aeris adraissione." Fund. Chem. dogmat. et 
ration, p. 22. 



Wi-.n.] THIRD DISSERTATION. 37 

daDcy over facts ; for it had been most satisfactorily de- 
monstrated by those experimentalists, that bodies will not 
burn if air be excluded, and that, during combustion, a 
portion of the air is consumed by the burning body. Even 
at an earlier period, the same observation had been most 
pointedly dwelt upon, and another equally important circum- 
stance ascertained, namely, the increase of weight sus- 
tained by metals during their calcination. As early as 
1629, Brun, an Apothecary, resident in the town of Ber- 
gerac in France, melted two pounds six ounces of tin, and 
in six hours the whole was converted into a calx, which 
weighed seven ounces more than the tin employed. Brun, 
surprised at this circumstance, communicated it to John 
Rey,^ a physician of Perigord, who, in 1630, published a 
Tract upon the subject, in which he refers the increase of 
weight to the absorption and solidification of air : '' Thus," 
says Rey, in the fanciful larsguage of the period, " have I 
succeeded in liberating this surprising truth from the dark 
dungeons of obscurity ; which was vainly but laboriously 
sought after by Cardan, Scaliger, Faschius, Caesalpinus, 
and Libavius. Others may search for it, but in vain, 
unless they pursue the royal road which I have cleared. 
The labour has been mine, — the profit is the reader's, — 
the glory is from above." 

But amongst the authors whose researches tended to 
conclusions diametrically opposite to those of Stahl and 
his associates, and whose writings abound in anticipations of 

* Essays de Jean Rey, DoctAir en Medecine, sur la Recherche 
dc la Cause pour laquelle VEstain et le Plornb augmentcnt de poids 
quand on les calcine''' Paris, 1777. 

Of these curious essays, originally ])rinted in 1630, a copy was 
discovered in the Royal Library at Paris in 1776. The scarcity 
of the first edition is in some measure accounted tor in the 
•^Advertisement" to the ()resent, but the rarity of this reprint is 
very enigmatical. 



38 THIRD DISSERTATION. [sect. ii. 

modern discoveries, no one stands so conspicuous as our 
countryraan John Mayow.* His tracts, published at Ox- 
ford in 1674, relating to chemical, physiological, and medi- 
cal subjects, abound in traits of original and inventive 
genius, and furnish the prototype of many discoveries, 
which have conferred great and lasting renown upon suc- 
ceeding labourers in the field of Chemistry. It is the 
treatise upon nitre and the nitro-aerial spirit to which I 
principally allude, and of which it may be proper to give a 
short but connected sketch. 

The atmosphere, he observes, contains a certain nitro- 
saline matter, a spirit, vital, igneous, and fermentative, 
which exists in, and may be obtained from nitre ; that it 
supports combustion, but is itself incombustible ; that it 
exists in nitrick acid ; that when antimony is exposed to 
the joint operation of heat and air, it imbibes the nitro- 
aerial particles, whence its increase in weight ; and that a 
similar change may be effected by nitre or by nitrick acid ; 
that acidity depends upon the absorption of the same prin- 
ciple which in sulphurick acid is combined with sulphur, 
either during combustion, or during the exposure of pyrites 
to air: that fermentation is referable to a very similar 
cause : that it is necessary to vegetation, and present in 
all cases of combustion; that it is absorbed by animals 
during respiration ; and that the same substance which 
contributes to the support of flame, is likewise required for 
the support of life. Mayow also was acquainted with the 

^ Mayow was born in Cornwall in 1645, and died in London 
in 1679, at the early age of thirty-nine. Dr. Beddoes and Dr. 
Yeats have asserted Mayow's claims to several modern discove- 
Fies ; and in many other instances than those quoted in the text, 
he has certainly anticipated both the discoveries and inventions 
of some of his chemical successors. AH Mayow's tracts are 
deserving of attentive perusal and are of full knowledge. The 
first and second, De Sal-nitro et Spirito Nitro-aerio and De Respi- 
ratione, contain a vast body of chemical facts, resulting from well 
conceived and conducted experiments. 



MCT.ii] , THIRD DISSERTATION. 39 

evolution of air during the action of nitrick and vitriolick 
acids upon iron, and points out a mode of collecting it, in 
bottles inverted in vessels of the dilute acids. He ob- 
serves that the air generated in these experiments, although 
expansible by heat, is probably different from the atmos- 
phere, as is also the air which an animal has breathed, and 
in which a candle has burned. 

These are a few of the important facts dwelt upon by 
Mayow, respecting the nature of the atmosphere, and of 
the cause of combustion. That they were not at the time 
opposed to the purely speculative notions of Stahl is truly 
remarkable, for they explain, in conjunction with the ob- 
servations of Rey and others, the great obstacle to the 
phlogistick hypothesis, the increase of weight in the burn- 
ing body ; they show the real cause of the necessity of the 
presence of air, which, if combustion consisted in the mere 
evolution of the subtile principle of fire, could not be re- 
quired ; and they adduced experimental evidence, where 
Stahl merely surmised. 

Another active inquirer occurs in this page of chemical 
history ; one whose researches cleared the way for the 
great discoveries of the succeeding era, and (o whom the 
merit is justly due of having opened a mine in the field of 
nature ; who indulged, not in the speculative and meta- 
physical frivolities which characterize tlie productions of 
most of his predecessors, and many of his contemporaries^ 
but followed nature with a steady and unerring step, and 
recorded his observations in a concise, unadorned and un- 
affected style. This was the Reverend Dr. Stephen 
Hales. ^ He was the first who instituted researches into 

'Born in 1677 ; died in 17G1. Dr. Hales is one of the few 
divines wlio have employed their abundant leisure in philosophi- 
cal and experimental researches. It is said that he refused high 
preferment upon more than one occasion, in order that he might 
attend to his humble parochial duties, and continue his scien- 
tifick pursuits. 



40 THIRD DISSERTATION. [sficr. ir. 

the physiology of vegetation, a subject which he pursued 
with considerable ardour and perseverance. He also made 
a variety of experiments upon the extrication of air during 
the exposure of animal, vegetable, and mineral substances 
to heat. In perusing his Essays on these subjects, we 
frequently find him upon the verge of those splendid dis- 
coveries which fell to the lot of bis fellow-labourers and 
successors ; but the erroneous nature of his preconceived 
opinions induced him to take for granted that which expe- 
riment should have determined, and to rest satisfied with 
results which, had they been followed up, would inevitably 
have led to the most important and novel facts. His experi- 
ments do credit to his industry, but his conclusions betray 
feebleness of judgment. If, instead of regarding the vari- 
ous gaseous products obtained from the substances he 
operated upon, as consisting of common air contaminated 
by their efiluvia, he had submitted them to more close in- 
vestigation, he would doubtless have run a more brilliant 
and successful career. He is justly regarded as the foun- 
der of Pneumatick Chemistry, but he contributed few ma- 
terials to the superstructure. 

Herman Boerhaave,^ of Leyden, who was a contempo- 
rary of Hales, pursued a similar train of inquiries ; but^ 

He directed his attention to the quantity of moisture imbibed 
and emitted by ofiSferent plants, and to the circulation of the 
sap, which, he says, put him upon making a more particular 
inq;>iiy into the nature of a flui<i which is so absolutely necessary 
for the suoport of the life and gri)wih of animals and vegetables. 

His Specimen of an Attempt to analyse the Air by Chymiostati- 
cal Experiments displays extraordinary ingenuity ia the contri- 
vance of experiments and apparatus. It was his misfortune to 
consider the vari >us gases which he procured as mere modifica- 
tions of atmospherick air. Plillos. Trans. Statical Essays, Lon- 
don, 1731. 

' Boerhciave was born in December 1668, at a village near 
Leyden. He died in September 1738. He was an eminent 



SBCT.n.] THIRD DISSERTATIdS-, 41 

although manj of his experiments were new and well con- 
ceived, he was not more happy in his conclusions, nor 
more fortunate in his discoveries. He attributed the elas- 
ticity of air to its union with fire, and considered its pon- 
derable matter as susceptible of chemical combinations ; 
but the existence of diflferent aeriform fluids escaped his 
notice. 

ornament of medicine, as well as of chemical science. Eis 
oration upon resigning the office of Governour of the University 
of Leyden has been justly eulogised by Johnson. (Life cf 
Boerhaave,) He here declares in the strongest terms (says his 
elegant biographer) in favour of experimental knowledge, and 
reflects with just severity upon those arrogant philosophers, who 
are too easily disgusted with the slow methods of obtaining true 
notions by frequent experiments, and who, possessed with too 
high an opinion of their own abilities, rather choose to consult 
their own imaginations than inquire into nature, and are better 
pleased with the charming amusement of forming hypotheses 
than the toilsome drudgery of making observations. 

The emptiness and uncertainty of all those systems, whether 
venerable for their antiquity, or agreeable for their novelty, he 
has evidently shown ; and not only declared, but proved, that 
we are entirely ignorant of the principles of things, and that all 
the knowledge we have is of such qualities alone as are dis- 
coverable by experience, or such as may be deduced from them 
by mathematical demonstration. 

Boerhaave's contributions to physick were large and valuable. 
His principal chemical work is the Elementa Chcmiae^ of which a 
good translation, with notes, was edited jo 1753 by Dr. Shaw^ 
This w^ork he dedicated to his brother, who was intended for the 
medical profession, but went into the church; while Boerhaave, 
who originally studied divinity, relinquished it for physick and 
chemistry. Alluding to this circumstance, " Providence," says 
he, "has changed our views, and consigned you to religious 
duties, while I, wliose talents were unequal to higher objects, am 
humbly content with the profession of physick." 

In the Elementa, and in several of his Orations, are admirable 
remarks upon the useful application of Chemislr}^ to other 
branches of knowledge. His observations upon its usefulness 
and necessity to the medical i^ractitioner, may be well enforced 
at the present day ; for, excepting in the Schools of London 
and Edinburgh, Chemistry, as a branch of education, is either 
entirely neglected, or, what is perhaps worso, siiperficiallv and 

8 



42 THIRD DISSERTATION. [stcx. ii. 

The philosophers whose names have been now recorded, 
not only greatly added to the stock of chemical facts col- 
lected by their predecessors, but conferred new life and 
vigour upon the science by their occasional incursions in- 
to the regions of theory and rational speculation : — in this 
light, the works of Rey, Mayow, and Stahl, deserve par- 
ticular attention ; the two former for correctness and pre- 
cision, the latter for boldness and ingenuity. 

About this period the Thermometer was brought to 
perfection, which tended materially to the progress of 
that most refined and diJflScult branch of Chemical Philoso- 
phy, relating to the nature and effects of heat. The re- 
searches, on this subject, will presently form an important 
feature in our history, which renders it proper to notice 
this instrument of such consequence in their prosecution. 

That bodies change in bulk, with variations of tempera- 
lure, must have been noticed at a very early period ; but 
there can be little doubt, that the idea of constructing an in- 
strument for measuring these variations first occurred to 
Santorio,^ Professor of Medicine, in the University of 
Padua, in the beginning of the seventeenth century ; he 
is also celebrated for his Medico-statical experiments, 
which are well burlesqued in one of the early numbers of 
the Spectator.^ 

imperfectly taught- This is especially the case at the English 
Universities, and the London Pharmacopoeia is a record of the 
want of chemical knowledge, where it is most imperiously re- 
quired. 

^ Santorio Avas born in 1561 at Capo d'Istria, on the borders 
of the Gulf of Trieste. He died at Venice in 1636. His 
At^s de Statica Medicina was published at Venice in 1 614. Much 
merit is due to the steady perseverance with which he opposed 
the occult remedies of the empiricks of his day. 

^ No. 25. By Addison. 



6ICT.1I.] THIRD DISSERTATION. 43 

Santorio's thermometer consisted of a tube, blown at 
one end into a bulb, and with the other open extremity 
immersed into water. In cold weather the confined air 
contracted and the water rose in the tube — in a warm at- 
mosphere the air expanded and the fluid fell. Santorio 
observed some other particulars connected with the opera- 
tion of this thermometer, among which the increased in- 
fluence of the sun's rays, when the bulb was blackened, 
deserves notice. 

The Academicians del Cimento, whose early labours 
have already been mentioned, materially altered and im- 
proved the thermometer, by employing a liquid to measure 
temperature, instead of air, the changes of bulk in which, in a 
moderate range of temperature, are so considerable as to ren- 
der the instrument extremely bulky and otherwise incon- 
venient. They generally used spirit of wine, and fixed a 
scale of degrees to the tube, with a view to ascertain its 
variations in bulk with greater precision. These instru- 
ments soon acquired considerable celebrity, and were 
largely circulated under the appellation of the Florence 
Glass. In this state the uses of the thermometer were ex- 
tremely limited, no two instruments corresponded, and 
there being a free communication between the fluid and 
the external air, it was liable to evaporation, — yet was this 
thermometer much preferable to the over-sensible and bul- 
ky instrument of Santorio. There was another objection 
to spirit of wine, arising out of the readiness with which 
it assumes an elastick state, and which renders it unfit for 
measuring temperatures even below the heat of boiling 
water. Sir Isaac Newton, therefore, suggested the use 
of linseed oil, which, however, is extremely ill adapted to 
the purpose, on account of its unctuosity, and the ease 
with which it solidifies. Quicksilver was first reconi- 



44 THIRD DISSERTATION* [sect. ii. 

mended by Roemer,' the eminent Danish philosopher, 
who discovered the motion of light ; it was also employed 
by Dr. Halley, and is now generally used. The advan- 
tages of this fluid metal in the construction of the thermo- 
meter are manifold ; it retains its liquid state at very high 
and very low temperatures, and has the peculiar excellence 
of expanding very equally for equal increments of heat, 
which is far from the case with spirit of wine. 

But the great improver of the thermometer was Fahren- 
heit,^ a merchant of Dantzic, who, having failed in busi- 
ness, and being attached to chemical and mechanical pur- 
suits, was obliged to gain a livelihood by making and selling 
these instruments. Fahrenheit used both spirit of wine 
and quicksilver, and hermetically sealed the tube contain- 
ing the fluid ; he also greatly improved the method of gra- 
duation, by establishing two points as the extremes of his 
scale, and subdividing the intermediate portion into a giv- 
en number of degrees. 

The division of the thermometrick scale had occupied 
the attention of several learned and ingenious men ; but 
it was Fahrenheit who pointed out the most accurate 
means of accomplishing this purpose. The curious cir- 
cumstance of the water running from melted snow being 
always of the same temperature, appears first to have oc- 
curred to Giiricke of Magdeburgh, but was first applied 
to the graduation of thermometers by Sir Isaac Newton, 
Dr. Hooke had observed that the quicksilver in the tube 
of the thermometer, plunged into boiling-water, always rose 
to the same height ; accordingly, if a mercurial thermome- 
ter be put into melting snow, and the point at which the 

* Born at Arhusen in Jutland, in 1644, — died at Copenhagen 
in 1710. 

^Born at Dantric in 1686,— died in 1724- 



SECT. II.] THIRD DISSERTATIO^^ 45 

fluid stands, marked upon the tube, and then transferred 
to boiling water, and that point also marked, and if the in- 
termediate space be subdivided into any number of equal 
degrees, 100 for instance, it follows that, provided proper 
precautions have been taken in selecting and filling the 
tube, every thermometer, so constructed, will indicate the 
same degree, when applied to bodies of the same tempe- 
rature. With regard to the boiling point, Fahrenheit ob- 
served it to diflfer under different degrees of atmospherick 
pressure, and pointed out the necessity of fixing it at a 
mean barometrical altitude. He had also noticed, that a 
degree of cold much more intense than that of ice might 
be procured by a mixture of snow and salt ; and conceiving 
this to be extreme cold, he commenced his scale from that 
point, which is 32*^ below the freezing of water. Accord- 
ingly, Fahrenheit's scale commences at 0*^, the tempeiature 
of his freezing mixture ; the freezing point of water is 
marked 32'^, and the boiling point 212*'; the space between 
the freezing and boiling of water being divided into 180*^. 
The graduation of thermometers received its greatest im- 
provement in 1742, by Celsius of Sweden, who commenc- 
ed the scale at the freezing of water, and divided the space 
between it and the boiling point into lOO''. This is 
the centigrade scale, now used in France. Reaumur's 
scale, in which the point of congelation is marked 0°, 
and that of boiling-water 80°, is used in some parts 
of the European Continent; and in Russia the descending 
scale of Delisle is sometimes employed, in which the boil- 
ing point of water is 0^ the freezing 1 jO*'. These scales 
have each their merits and defects. In the event of inno- 
vation, the interval between the freezing and boiling of 
mercury, might be divided into 1000 equal parts; the for- 
mer being 40' below 0^ of Fahrenheit, the latter about + 
670^ The degrees would thus be sufficiently small to be 
expressed without fractions ; and the coinmencement of 



46 THIRD DISSERTATION* [sRcr. u. 

the scale, which is about the lowest natural temperature, 
would be so low, as to preclude the frequent necessity of 
expressing negative degrees.* 

From this sketch of the history of the thermometer, 
it is obvious, that its operation depends upon the circum- 
stance of fluids diminishing in bulk by diminution of tem- 
perature, and the contrary; which is really the case with 
all fluids except water. This important fact was observ- 
ed by the Florentine Academicians in their early experi- 
ments, and it is among the most curious and interesting 
discoveries of that zealous and active association of expe- 
rimentalists. Having filled a large thermometer tube with 
water, they plunged it into a mixture of salt and snow. 
The water presently began to contract in bulk, and de- 
scend in the tube ; but, instead of continuing to do so, 
till it reached the freezing point, after a short time it com- 
menced expanding ; the expansion went on till a portion 
of the water froze, and was then very suddenly increas- 
ed.2 

* This proposal is suggested by Mr. Murray. System of Chem- 
istry^ Vol. I. 

^ The following unafifected narrative of this celebrated ex- 
periment is very different from the usual verbose and pompous 
style of the philosophers of the period. 

" Gia sapevamo per innanzi (e lo sa ognuno) che i! freddo da 
principio opera in tutti i liquori restrignimento, e diminuzione 
di mole, e di cio non solamente n'avevamo la riprova ordinaria 
deli' aquarzente de' Termometri, ma n'avevamo fatta esperi- 
enza neil' acqua, nelP olio, nell' argentovivo, ed in molt' altri 
fluidi. Dair altro canto sapevamo ancora, che nel passaggio, 
che fa Tacqua dall' esser semplicemente fredda al rimuoversi 
dalla sua fluidita, e rlcever consistenza, e durezza coll' ag- 
ghiacciamento non solo ritorna alia mole, ch' ell' aveva prima 
di raffreddarsi, ma trapassa ad una maggiore, mentre se le 
veggon rompere vasi di vetro, e di metallo con tanta forza. 
Ma qual poi si fosse il periodo di queste varie alterazioni, che 
in essa opera il freddo. questo non sapevamo ancora, ne era 



9MCT.U,] THIRD DISSERTATION. 47 

The temperature at which water thus begins to expand 
by cooling is 40® Fahrenheit, and water cooled down to 
32% that is, 8*^ below 40% occupies the same space as 
when heated to 8® above 40°; in other words, the density 
or specifick gravity of water is at its maximum at 40^ 

When in the year 1683 Dr. Croune repeated this ex- 
periment before the Royal Society, Hooke attributed the 
effect, not to any peculiarity in expansibility of water, 
but to a rapid and sudden contraction of the glass bulb, 
which would force the water upwards in the tube ;' a con- 

possibile d'arrivarvi con agghiacciarla dentro a' vasi opacbi, 
come quel d'argento, d'ottone, e d'oro'ne' quali s'era fin' allora 
agghiacciata : Onde per uon mancare di quella notizia, cbe 
parea esser I'anima di tutte quest' esperienze, ricorremmo al 
cristallo, ed al vetro, sperando per la transparenza delta mate- 
ria d'aver presto ad' assicurarci come la cosa andasse, raentre 
si poteva a ciascun movimento, cbe fosse apparso nell' acqua 
del collo, cavar subito la palla dal' ghiaccio, e riconoscer in 
essa quali alterationi gli correspondessero. Ma la verita si 
e, che noi stentammo assai piu che nou ci saiemmo mai dati 
ad intendere, prima di poter rinvenire alcuna cosa di certo 
intorno a' periodi di questi accidenti. E per dime piu dis- 
tintamente, il successo e da sapere, che nella prima immer- 
sione, che facevamo deiia palla, subito, ch'ella toccava i'acqua 
del ghiaccio s'osservava nell' acqua del collo un piccolo sol- 
levamento, ma assai veloce, dopo il quale con moto assai ordi- 
nato, e di mezzana velocila s'andava retirando verso la palla, 
finche arrivata a un certo grado non proseguiva piu oltre a 
discendere, ma si fermava quivi per qualche tempo, a giudizio 
degli occhi, offatto priva di movimento. Poi a poco a poco 
si vedea ricomiuciare a salire, ma con un moto tardissimo, e 
apparentemente equabile, dal quale senz' alcun proporzionale 
acceleramento spiccava in un subito un furiosissimo sulto, nel 
qual tempo era impossibile tenele dietro coif occhio, scorreudo 
con quell' impeto, per cosi dire, in istanti le decine e le decine 
de' gradi." Espenenzc intorno al pro<(resso darli artiflziaU a^'- 
srhiacciamcnti, c dc' loro mirahill accidenti. Saggi di natnrali 
esperienze fatte nelT accademia Del Cimentu/' Firenze, 
1001. 

* The Jlislorics of tfu Royal Society by Sprat and Birch, con- 
lain a curious body of experimental evidence ou a great varie- 



48 THIRD DISSERTATION. [sect. !x. 

elusion amply disproved by other forms of the experi- 
ment, especially by that suggested by Dr. Hope^ of Edin- 
burgh, in which a freezing mixture was applied to the sur- 
face of water at 60^ contained in a tall cylindrical glass jar. 
The water was cooled throughout to 40°, and then the sur- 
face sunk to 32^ and froze. But when the freezing mix- 

ly of philosophical subjects, and detail the opinions and ob- 
servations of many eminent persons upon the various researches 
that were carried on before that learned body. The business 
of the Society was formerly conducted upon a very dififerent 
plan from that now pursued, and much resembled the present 
proceedings of the Academy of Sciences of the Royal Insti- 
tute of France. 

The following is Dr. Birch's memorandum relating to this 
experiment : 

February 6, 1683. 

A letter of Mr. Musgrave to Mr. Aston, dated at New Col- 
lege, Oxford, was read, containing, among other things, several 
experiments about freezing, as that two inches of water in a 
tube 4 inch diameter, ex|?anded itself, upon freezing, |- high- 
er ; that a tube one inch diameter filled 6 inches, rose upon 
freezing, i of an inch; Bnd that halt a pint of water, upon freez- 
ing, lost in weight 3ij. Bij. gr. viij. 

Dr. Croune said, that having weighed three ounces of water, 
he found it, after freezing, to differ a scruple and a half. 

Sir Christopher Wren remarked, that if water were suddenly 
frozen, there would be less difference in weight. 

Dr. Croune said, that he observed water which he had put 
into a bolt-head, to rise higher before there was any thing of 
freezing in it. 

Mr. Hooke attributed the rising of the water in the neck of 
the bolt-head, to the shrinking of the glass. 

Dr. Croune said, that t.he ghiss had been long in the cold be- 
fore, and thrit the water rose immediately. 

Dr. Wallis [jroposed, that an empty glass might be cooled well 
in a freezing liquor, in order that it might have its contraction 
before the water bf put into it. 

This was done immediately by Mr. Hunt, and the water be- 
ing put into a small bolt-head, rose about ** of an inch in the neck, 
though the air at that time was very warm. (Birch's Historic 
of tlie Royal Society, Vol. IV. p. 253.) 



' Edinburgh Transactions^ Vol. VL 



McT.ii.] THIRD DISSERTATION, 49 

ture was applied to the bottom of the jar, the water be- 
came cooled throughout to 32^ If the cold be applied 
to the centre of the vessel, as long as the water is above 
40^ the warmer part will always be at the top, but below 
40*^ the arrangement is reversed, and the warmer part be- 
ing then most dense, occupies the lower half of the vessel, 
and the colder portion floats upon it. 

The influence of this singular anomaly, which has thus 
been demonstrated by unanswerable experiments, is of 
great extent and importance. In most of the cases in 
which nature deviates from her usual established laws, 
philosophy has discovered happy consequences in her ab- 
erration ; and where such discovery has not been made, 
investigation should be upon the alert (o trace the clue 
that is presented. 

If water were obedient to the same laws of refrigeration 
as other less universal liquids, such as spirit, oils, and 
quicksilver, it must be evident, that, during the winter's 
cold, our rivers and lakes, instead of presenting a superfi- 
cial stratum of ice, would soon become solid throughout; 
the continuous influence of the summer's sun would be re- 
quired to produce their fluidity, and the inhabitants of the 
waters would annually risk exiermination. 

These effects are obviated by the peculiarity observed 
by the Academicians del Cimento. As the temperature 
of the earth is in winter always greater than that of the 
atmosphere, the cooling of large bodies of water must 
take place from above, by the contact of cold air and 
chilling blasts. The whole mass will thus be lowered to 
40*^, after which, the water becoming specifically lighter 
as it becomes colder, remains upon tjie surface where it 
sinks to 32^, and is converted into a film of ice, which 
being a bad conductor of heat, thickens slowly, and affords 
further protection to the warmer fluid beneath. Those 

7 



so THIRD DISSERTATION. [sect. ii. 

who in winter's cold accidentally fall through the ice, are sur- 
prised by the comparative warmth of the water below, 
and the aquatick animals that in summer sport upon the 
surface of their element, retire in winter to the more ge- 
nial retreats which nature has thus provided. 

In tracing the progress of Chemistry through its dark 
and early periods, the historian necessarily traverses a rug- 
ged and barren path ; his chief object must be to advance, 
and the shortest is generally the safest road. Reaching 
the age of Alchemy, the prospect, though improved, is 
not such as to demand a very deliberate survey : its fictions, 
however, like those of romantick chivalry, have some- 
what of reality for their basis, and by the mere increase 
of experimental inquiry, contributed essentially to the 
growth of chemical knowledge. As a science, its pro- 
gress was languid until the middle of the seventeenth cen- 
tury, when it began to shake off the lethargy in which it 
had been sunk, and was turned with eager curiosity to new 
and more useful objects. 

In the dross of the alchemical furnaces many scattered 
treasures were discovered, the value of which was great- 
ly enhanced by arrangement and systematick combination. 
New views were thim opened to the Experimentalist; 
and authors, dismissing the florid exuberances and pom- 
pous affectation of their predecessors, cultivated an un- 
adorned and simple style, more becoming the dignity of 
scientifick narration. 

These circumstances contributed to confer a prosper- 
ous aspect on Chemical Philosophy at the commencement 
of the eighteenth century. It was applied to the arts, 
and to them i( gave an unexpected and vigorous impulse. 
It was directed to the investigation of nature, and there 
it discovered new beauties. It found '' tongues in trees, 
books in the running brooks, sermons in stones, and good 
in every thing." 



SECT. III.] THIRD DISSERTATION. 5] 

SECTION III. 

DISCOVERIES OF DR. BLACK, RELATING TO THE CAUSE OF CAUSTICITY" 
IN EARTHS AND ALKALIES, AND TO CERTAIN PHENOMENA OF HEAT. 

The discoveries of Dr. Joseph Black form a most im- 
portant epoch in the history of Chemical Philosophy ; 
thej embrace two leading subjects, — the one relating to 
the causticity of the earths and alkalies — the other to the 
operation of heat in changing the state of bodies ; in ren- 
dering solids liquid ; and converting liquids into elastick 
or aeriform fluids. 

Regarding these researches as isolated specimens of in- 
ductive philosophy, they have rarely been equalled: as 
influencing the progress of Chemistry, by disclosing the 
hidden cause of many very intricate phenomena, they have 
never been surpassed ; and, by a happy combination of 
circumstances, we trace in them the distant but fertile 
source of those gigantick improvements of the arts, in 
which the perfection of the steam-engine is involved. 

Of a man whose scientifick character is thus pre-emi- 
ment, and in whose attainments his country has just reason 
to exult, history has recorded a brief but interesting me- 
morial.' 

Dr. Joseph Black was sprung from a Scottish family, 
transplanted first to Ireland and then to France, where 
he was born in 1728, on the banks of the Garonne. When 
twelve years of age, he was sent for education to Belfast, 
and afterwards to the University of Glasgow, where he 
entered upon the study of physick, under the guidance of 
that bright ornament of medical science, Dr. William Cul- 
len. In 1750, he removed to Edinburgh; four years af- 

* Dr. Robison's Preface to Black's Lectures on the Elements of 
Chemistry, 



52 THIRD DISSERTATION. [sect. in. 

terwards, be took Ihe degree of Doctor of Physick ; and, in 
1756, published his Experiments on Magnesia, Quicklime, 
and some other alkaline substances, in the Physical and Lit- 
erary Essays. In the same j^ear, Dr. Cullen having remov- 
ed to Edinburgh, Dr. Black returned to Glasgow to fill the 
Medical and Chemical chair of that University, where he 
was received with open arms both by the Classes and Pro- 
' fessors. In 1764, he brought his ideas respecting the com- 
binations of heat with ponderable matter to perfection. 
Speculations upon this subject had occupied his mind dur- 
ing a considerable period, but the difficulties of the in- 
quiry, and the time necessarily consumed in other pro- 
fessional avocations, had considerably interfered with the 
pursuit. 

In 1766, he was appointed to the Chemical Chair of Ed- 
inburgh, an office which he filled with such talent, indus- 
try, and perseverance, as not only drew an immense con- 
course of hearers to his class, but tended to confer upon 
chemistry a degree of popularity and importance, which 
has been greatly conducive to its promotion and extension, 
^^His discourse," says his biographer. Professor Robison, 
"was so plain and perspicuous, his illustrations by experi- 
ment so apposite, that his sentiments on any subject never 
could be mistaken; and his instructions were so clear of 
all hypothesis or conjecture, that the hearer rested on his 
conclusions with a confidence scarcely exceeded in mat- 
ters of his own experience."^ In short, Dr. Black, in his 

* Dr. Black's character as a lecturer, is given by his friend 
Professor Robison in the following terms : — " He endeavoured 
every year to render his courses more plain and familiar, and 
to illustrate them by a greater variety of examples in the way 
of experiments. No man could perform these more neatly and 
Bucceesfully. They were always ingeniously and judiciously 
contrived, clearly establishing the point in view, and never 
more than sufficed for this purpose. While he scorned the 



MCT.in.] THIRD DISSERTATION. 53 

professorial capacity, was entitled to every praise, and he 
contributed most essentially to the foundation and increase 
of the reputation which the University of Edinburgh has 
acquired and maintained. Nor was his private character 
at variance with his publick excellence; he was mild, amia- 
ble, and fond of conversation, whether serious or spor- 
tive ; and he was not above uniting to the highest philoso- 
phical attainments, most of the elegant accomplishments of 
life. In his advanced age he often expressed a hope that 
he might not linger in protracted sickness, on account of 
the distress which, in such cases, is suffered by attend- 
ing friends ; and his death, which happened in his 7lst 
year, in November 1799, is on this account the more re- 
markable. He was taking some milk and water, and hav- 
ing the cup in his hand, when the last stroke of his pulse 
was to be given, had set it upon his knees, and in this 
attitude expired without the smallest agitation. 

The writings of Black, though lamentably few, are mas- 
terpieces of scientifick composition. Newton was his 
model, and he was the iBrst who transferred into chemis- 
try the severe system of inductive logick, which marks 
the productions of that great master of natural philosophy. 

quackery of a showman, the simplicity, neatness, and elegance 
with which they were performed, were truly admirable. In- 
deed, the simplex mimdiiiis stamped every thing that he did. I 
think it was the unperceived operation of this impression that 
made Dr. Black's lectures such a treat to all his scholars. They 
were not only instructed, but (they knew not how) delighted; 
and without any effort to please, but solely liy the natural emana- 
tion of a gentle and elegant mind, co operating indeed with a 
most perspicuous exhibition of his sentiments. Dr. Black became 
a favourite lecturer, and many were induced, by the report of 
his students, to attend his courses, without having any particu- 
lar relish for chemical knowledge, but merely in order to be 
pleased. This, however, contributed greatly to the exteuding 
the knowledge of Chemistry, and it became a fashionable part 
of the accomplishments of a gentleman." Preface^ p. 11 



54 THIRD DISSERTATION. [sect. in. 

" In no scientifick inquiries, since the date of the Princi- 
pia and Opticks^ do we find so great a proportion of pure 
ratiocination, founded upon the description of common 
facts, but leading to the most unexpected and important 
results, as in the two grand systems of Black.'' Averse 
to all hypothesis, and aware of the multitudinous facts 
upon which a theory that is to stand firm must be found- 
ed. Dr. Black was unwarrantably slow in the formal pub- 
lick disclosure of his admirable researches. His tenets 
were fully and freely delivered to his pupils ; but he very 
rarely intruded upon the publick as an author ; and his 
splendid achievements in the philosophy of heat are chiefly 
developed in his posthumous works. This silence, aris- 
ing out of an over-cautious modesty which marked all his 
proceedings, was not favourable to the reputation of Dr. 
Black. Faulty and incomplete copies of his lectures 
were circulated among his friends and admirers, which af- 
terwards reached the hands of those who deserve another 
name, and by whom they were not very honourably em- 
ployed. 

The first researches of Dr. Black, which it will be ne- 
cessary to attend to, explain the cause of causticity in 
earths and alkalies. When chalk or limestone, which are 
mild insoluble tasteless substances, are heated to redness 
in the open fire, they are converted into quicklime, a body 
corrosive, soluble in water, and having an acrid flavour. 
Stahl, Macquer,' and Meyer, attributed this change to 

1 Macquer was born at Paris in 1718, and died in 1784. He 
ranks among the most eminent scientifick Chemists of the early 
part of the eighteenth century ; and though involved in the errours 
of the Phlogistick school, he has written with much good sense 
and perspicuity on a variety of chemical subjects. His most cele- 
brated works are, the Elemens de Chimie Theorique, Paris, 1 749 ; 
^udElemem de Chimie Pratique, Paris, 1751. He also published 



3BCT. III.] THIRD DISSERTATION. 55 

some substance absorbed from the fire, — to an acrid acid,^ 
— to phlogiston, and other creatures of the imagination. 
Dr. Black's mind was turned to this subject in consequence 
of the discovery of magnesia. This substance made its 
first appearance as an Arcanum in Italy, in 1707. Valen- 
tine showed that it might be obtained from the mother-li- 
quor of nitre, but it was supposed to be lime, until Hoff- 
man, in 1720, pointed out several peculiarities by which 
it is distinguished from that earth. Hoffman prepared 
magnesia from bittern, or the saline liquor which remains 
after the separation of common salt from sea water; to this 
he added an alkali which precipitated the earth.^ The 

a Chemical Dictionary. The following is all his information 
respecting the property possessed by quicklime of rendering the 
alkalies caustick. After describing the process, he observes, " Le 
but de cette operation, est de reunir avec le sel alcali fixe ce que 
la chaux a de salin et d'acre." '' On le combine avec la par- 
tie la plus acre, la plus subtile, et la plus saline de la chaux." 

"Nous n'entreprendrons point ici d'expliquer pourquoi le 

sel alcali, que Ton combine avec la chaux, acquiert une si gran- 
de causticite. Cette question nous paroit une des plus deiicates 
et des plus difficile s a risoudre que nous offre la Chimie, Elle tient 
a celle des proprietes alcalines de la chaux, et on ne peut gueres 
esperer de la resoudre, que quand on aura acquis sur la nature de 
cette substance, beaucoup plus de lumieres que nous n'en avons 
a present." Elenuns de Chimie Pratique, pp. 1 79. 182. 

* J. F. Meyers, Chemische versuche zur ndhern erkenntniss des 
ungeloschten kalks ; der elastischen und electrischen Mater ie, des al- 
lerreinstcn fcuerwesens, und der ursprunglichen allgemcinem sdure. 
Hannover, 1764. In this dissertation, though published sub- 
sequently to Black's essay, the causticity of the alkalies and 
lime is referred to the absorption of a principle which the author 
calls Caustiami, or Acidum pinguc. Between the years 1 760, 
and 1 772, a great variety of dissertations were published in 
Germany upon this question, some in support of Black's doc- 
trine, others in favour of Meyer's hypothetical absurdities. See 
Gren's Systcmatischcs Handbuck der Qcsammicn Chemie, Halle, 
1794. § 437. 

^ Obscrv. Phys^ Chcm. 1 722. 



56 THIRD DISSERTATION. Isect. ni. 

substance which thus exists in bittern, is a compound of 
magnesia and sulphurick acid. It was first obtained from 
certain mineral springs in the neighbourhood of Epsom in 
Surry, and thence called Epsom salt, but was sold at a very 
high price, in consequence of the small quantities so pro- 
cured, until the manufacturers in the neighbourhood of 
Lymington obtained it from sea water ; it was then largely 
exported to the Continent under the name of English salt. 

Epsom salt was indeed long confounded with Glauber's 
salt, and a fraud of the manufacturers here, and in Germa- 
ny, tended to keep up the confusion ; for at that period 
Glauber's salt was rare in England, and large crystals of 
Epsom salt were sold under that name ; but in Germany, 
where Epsom salt was not common, Glauber's salt, in 
small crystals, was vended as English or Epsom salt. Pott 
of Berlin, and Du Harael of Paris, were led into a comedy 
of errours in consequence of mistaking the nature of these 
bodies. 

Dr. Black found that, when magnesia was prepared by 
precipitating a solution of Epsom salt by a mild alkali, 
that it effervesced with acids ; but that when heated to 
redness, it lost weight, and then dissolved without etfer- 
vescence. This fact, which also holds good in respect to 
lime, induced him to believe that, instead of gaining any 

Hoffman was the most celebrated Chemical Physician of the 
age. He was born at Halle in Saxony, in 1660, and died in 
1742. His writings, which are voluminous, are also valuable. 
In 1749, they were eked out by the Geuevese Booksellers into 
nine folio volumes. The following are his leading Essays in 
Chemistry : 

Dissertationes de Generatione Salium, — De Natura Nitri, — Be 
Cinnabare Antinionii, — De Mirabili Sulphuris Antimonii jixaii 
efficacia, — De Mercurio et Medicamentis Mercurialibus. Obser- 
vationwn Physico-Chemicarum Collectio. Libri iii. 



«icT.iii.] THIRD DISSERTATION- 57 

thing in the fire, something was lost by these earths. He, 
therefore, distilled some magnesia in a retort, but found, 
that although it lost weight as before, nothing but a rela- 
tively small quantity of water was found in the receiver. 
The experiments of Dr. Hales now rushed into his mind, 
and it occurred to him, that some gaseous or aeriform 
body had escaped from the earth, and that this was the 
cause of its effervescing with acids, — a circumstance pre- 
viously ascribed to the collision of the acid and earthly 
particles. He therefore put some magnesia, not calcined, 
into a bottle, with a bent tube attached to it ; and thus, 
during the action of the acid, obtained a large quantity of 
an elastick fluid, in a vessel inverted in water ; he found, 
too, that chalk, and common alkali, yielded ihe same kind 
of air. The air thus existing in these substances Drc 
Black called fixed air ; and he proved it to be the cause 
of mildness in earths and alkalies. If lime be added to a 
mild alkali, the lime absorbs its fixed air, and renders it 
caustick, — an effect formerly attributed to the transfer of 
the fiery particles of the lime. 

In the year 1750, Venel observed that Sellers, and 
other sparkling waters, when placed under the receiver of 
an air-pump, gave out a large quantity of air, and became 
flat and insipid, and he imitated them by dissolving com- 
mon soda in water, and adding muriatick acid, which pro- 
duced an effervescence and gave it brisknessJ These 
experiments were a little antecedent to Ur. Black's pub- 
lication, but they by no means anticipated his discover- 

' " Kn 1750, Venel, Professenr de Chiinie a Montpclller, re- 
prit le til de ses experiences en arrc(aut dans I'eau le fluide 
degage des effervescences, cl en imitant ainsi, par sa dissolution 
artificieilf^, Ics caux niincralcs aei^lules ; mais il fit encore ious 
ses efforts pour prottvcr que cctoit de Cair:' Fourcrov, His- 
ioire, p. 28. 

a 



58 THIRD DISSERTATION. [sict. ly. 

ies.* In 1764 the conclusions of Black were verified, and 
his views extended, by Dr. Macbride of Dublin, who 
pointed out several new properties of fixed air, and de- 
monstrated its existence in the atmosphere ; for lime ex- 
posed to air gradually loses its causticity, and becomes 
effervescent. The operation of quick-lime as a manure 
depends upon its power of rendering the inert vegetable 
matter of the soil soluble, and fit for the nourishment of 
young plants ; an effect which it does not produce when 
combined with fixed air, or in the state of chalk : hence 
the lime should be spread quickly over the land, and not 
left in heaps exposed to the air, by which, as Dr. Mac- 
bride has shown, it is rendered mild, and of comparatively 
small effect.^ 

* Dr. Brownrigg of Whitehaven threw out some curious hints 
respecting fixed air, or, as it is now called, carbonick acid, as 
early as 1765. In a communication to the Royal Society, 
printed that year in their Transactions, he remarks, " that a 
more intimate acquaintance with those noxious airs in mines, 
called damps, might lead to the discovery of that subtile princi- 
ple of mineral waters, known by the name of their 6^;;?n/ ; that 
the mephiiick exhalations termed the Choak damp, he had found 
to be a fluid permanently elnstick; and, from various experi- 
ments he had reason to conclude, that it entered the composi- 
tion of the w aters of Pyrmont, Spa, and others, imparting to 
them that pungent taste, from which they were denominated 
acididae, and likewise that volatile principle on which their 
virtues chiefly depend." 

Mr. Lane was the first who ascertained the solubility of iron 
in water, impregnated with fixed air. Fhil. Trans, 1769. " By 
this means," says Sir John Pringle in his discourse on the dif- 
ferent kinds of Air, delivereci at the anniversary meeting of the 
Boyal Society, November 30, 1773, *' the nature of the metal- 
lick principle in mineral waters was clearly explained, and the 
whole analysis of those celebrated fountains, so often attempted 
by Chemists and others, and still eluding their laboured re- 
searches, was thus, in the most simple manner, brought to 
light." 

^ M9.chx\{\^'^ Experimental Essays, 1764. The merit of this 
performance induced the University of Glasgow to bestow the 
degree of Doctor of Pbysick on the author. 



BF.cT. 111.] THIRD DISSERTATION. 59 

Such are the principal features of Dr. Black's researches 
respecting the cause of mildness and causticity in earth/ 
and alkaline substances. They constitute an important 
body of chemical evidence, and are established upon the 
satisfactory basis of analytick and synthetick proofs. 

I now turn to his more elaborate investigation into the 
effects of heat ; to inquiries so momentous in their in- 
fluence upon the advancement of experimental philosophy, 
so replete with difficulties, and so masterly in their execu- 
tion, as to raise them to the highest efforts of the human 
mind. I have deemed a rapid glance at the discovery of 
fixed air sufficient for our present purpose ; for occasions 
will afterwards offer of descanting more largely upon its 
nature and properties ; but the investigation now before us, 
is that from which the towering and durable greatness of 
Black's name has been principally derived ; and it was 
begun, continued, and completed, by the labour of his own 
hands. 

In speaking of the graduation of thermometers, it was 
mentioned, that if snow or ice be brought into a warm at- 
mosphere, and suffered to thaw slowly, the water which 
runs from it is always at one temperature, that of 32° of 
Fahrenheit's scale. This and similar cases seem to have 
occupied the early thoughts of our philosopher ; for his 
biographer informs us, that, in the oldest pyarcels of his 
notes, he found queries relating to this subject. How 
does it happen that, although heat is constantly flowing 
from surrounding bodies to the ice, its temperature is not 
increased ? Water at 32^ when brought into a room at 
60^ goes on increasing in temperature till it attains that of 

Dr. Macbride introduced some important improvements into 
the art of Tanning, and was the first who em()loyed lime 
water in the prefiaratory operations of that process. He was 
born in the county of Antrim in 1720, and died in 1778. 



60 THIRD DISSERTATION, [sect. in. 

the circumambient air ; but the ice, though exposed to ex- 
actly similar sources of heat, remains at 32^ Why, when 
water is cooled several degrees below its freezing point, 
does its temperature suddenly rise to that point, the instant 
that it congeals? or why is it, that, when a vessel of water 
is put upon the fire, a thermometer plunged into it con- 
tinues to indicate increase of heat until it rises to 212®; 
and the water then boils, but does not become hotter, al- 
though it remains upon the fire, and has all its former op- 
portunities of acquiring heat ? Such were the queries 
which Dr. Bidck has most happily resolved. 

In regard to the liquefaction of ice, he has demonstrat- 
ed that, when solids pass into the liquid state, the change 
is always accompanied with the absorption of heat, which 
is concealed or becomes latent in the liquid, and is not in- 
dicated by the thermometer, which instrument, therefore, 
is no measure of the absolute quantity of heat. A variety 
of interesting and curious experiments were undertaken 
with a view to ascertain the quantity of thermometrick heat, 
which thus becomes latent during the conversion of ice 
into water. A pound of snow at 32^ was mixed with a 
pound of water at 172*; the snow was melted, and the 
temperature of the mixture was only 32^ ; so that here 
140^ thermometrick heat had disappeared ; their effect 
being, not tot raise the temperature of the snow, but to 
convert it into u^ater. We should say, therefore, from 
this experiment, that water at 32^ is a compound of ice, 
and 140^ of heat as indicated by the thermometer. If wa- 
ter, at the tcQiperature of 32% be mixed with an equal 
weight of warm water, suppose at 200°, the resulting tem- 
perature will be the mean ; 232 -f- 2 = 1 16 ; but if we use 
ice, the temperature will not be the mean, for 140® of heat 
must be substracted from the warm water, which heat is 
consumed in liquefying the ice ; the result, therefore, will 



sicT.iii.] THIRD DISSERTATION. 6l 

be the same as if water at 32® and 60<^ were mixed, giving 
a mean of only 45®. 

These experiments at once demonstrated the cause of 
many facts respecting the production of heat and cold, 
which, though long known, remained without any plausible 
explanation. 

When solids become fluids, the production of cold is 
more or less evident, according to the rapidity of the 
change. Those saline bodies, for instance, whicb are 
"Very rapidly soluble in water, generate during their solu- 
tion a considerable intensity of cold, for to become fluid 
they must absorb heat. When snow and salt are suddenly 
blended, there is an instant liquefaction, and the tempera- 
ture of the substances being already low, a degree of cold 
equal to 0° of Fahrenheit is obtained The production of 
cold by mixing snow and muriate of lime, a very soluble 
salt, is — 40® Fahrenheit, and suflScient to freeze quick- 
silver even in a comparatively warm atmosphere. A mix- 
ture of 5 parts of sal ammoniack in powder, and 5 parts of 
nitre with 16 of water, sink the thermometer from 60° to 
10®. Equal parts of nitrate of ammonia, and water, pro- 
duce a more intense cold, and by a clever successive ap- 
plication of these freezing mixtures, the intense degree of 
cold of — 91® Fahrenheit has been artificially exhibited. 
This is 123® below the freezing of water, and 40® the great- 
est natural cold hitherto observed, which was at Hud- 
son's Bay, where the spirit thermometer has been seen 
at 50®^. 

There are many counter illustrations of this doctrine of 
latent heat; in which heat is evolved during the conver- 
sion of liquids into solids. If oil of vitriol be poured upon 
magnesia, there is a sudden solidification of the acid by 
its union with the earth, and a considerable rise of tem- 
perature ensues. Water poured upon quicklime produces 



62 THIRD DISSERTATION. [srct. iii 

a similar phenomenon ; and when water at perfect rest is 
exposed in a covered vessel to an intensely cold atmos- 
phere, its temperature may be reduced to many degrees 
below its freezing point : A slight agitation causes it sud- 
denly to become ice, and at that instant the temperature 
rises to 32°. A somewhat similar case is the sudden crys- 
tallization of saline solutions, during which their latent 
heat becomes sensible to the feeling, and is indicated by 
the thermometer. 

In Dr. Black's theory of latent heat, it is assumed that 
heat is matter; that it is a substance of excessive tenuity, 
existing in variable proportions in bodies ; that when in a 
free state, it affects our senses, and the thermometer, but 
that it occasionally enters into union with other substances, 
or is separated from them, consistent with the usual laws 
of chemical attraction. Thus, in fluids, it is combined 
or latent, but when they are converted into solids, it is 
separated in a free or sensible slate. The other view of 
the question represents heat as the result of a vibrating 
motion among the particles of bodies ; the vibrations be- 
ing most rapid and extensive in the hottest bodies. In 
fluids the vibrations are accompanied by a motion of the 
particles round their own axes ; and when solids pass into 
the fluid state, the vibratory motion or temperature is in 
part lost, by the communication of the rotatory motion to 
the particles. Each of these hypotheses has had its able 
defenders and advocates ; the ideas of Newton seem to 
have been favourable to the latter, and manj facts may be 
adduced in its support. The strongest are the imponde- 
rability of heat, and its continuous extrication by fric- 
tion. That we discover no increase of weight in a heated 
body may be attributed to the insuflSciency of our in- 
struments, but its unlimited production in a variety of 



81CT.1II.] THIRD DISSERTATION. 63 

easeS) though consonaDt with the hypothesis of vibration, 
ill agrees with that of a specifick form of matter. 

If a soft iron nail be beaten upon the anvil, it becomes 
hot and brittle, and it cannot again be rendered malleable 
till it has been reseftened by exposure to the fire. By 
those who favour the notion of a matter of heat, this has 
been called an experimentum crucis. The matter of heat, 
say they, is squeezed out of the nail, as water out of a 
sponge, but it is reabsorbed in the fire. In this experi- 
ment, however, it must be recollected, that the mechani- 
cal arrangement of the particles of the iron is considerably 
altered ; it is rendered very brittle ; and hence, perhaps, 
its insusceptibility of becoming again hot, till restored to 
its former state or texture by the expansive power of fire. 

It was not until the publication of the researches which 
have just been considered, that a variety of curious cir- 
cumstances concerning congelation were understood. The 
gradual progress in the freezing of large bodies of water 
has been shown to depend in some measure upon the re- 
markable anomaly respecting its maximum of density ; 
but it is also materially connected with the phenomena of 
latent heat ; for water, before it can become ice, must 
part with a quantity of heat, which if suddenly evolved, 
would raise the thermometer 140^ It must also be ob- 
vious, that the process of thawing suffers a similar retarda- 
dation, for ice requires for its conversion into water, the 
absorption of 140^ of sensible heat. 

Thus we see that sudden congelation and sudden lique- 
faction are alike prevented ; that the process must be 
gradual, and consequently productive of none of those 
evils which would result from a more rapid change. 

One of the great advantages of irrigation, or meadow 
watering, is also explained by a reference to these princi- 
ples. In an irrigated meadow, the surface of the water 



64 THIRD DISSERTATION. 



[SBCT. 



may be frozen ; but as water at 40° is heavier than at 32^, 
the former will be its temperature in contact with the grass ; 
and it is a temperature perfectly congenial to the functions 
of vegetable life. Sir Humphrey Davy examined the 
temperature in a water meadow near Hungerford, in Berk- 
shire, by a very delicate thermometer. The temperature 
of the air, at seven in the morning, was 29^. The water 
was frozen above the grass ; the temperature of the soil 
at the roots of the grass was 43^ Thus, by the peculiari- 
ty in the refrigeration of water, by the defence afforded 
by the stratum of ice, and by the laws of congelation, the 
vegetables are not merely protected from the effects of 
an intensely cold atmosphere, but likewise from the inju- 
rious influence of sudden changes of temperature. 

Congelation is to surrounding bodies a source of heat^ 
and there is no inconsiderable mitigation of the extreme 
cold of air wafted over large bodies of water, by the trans- 
fer of latent to sensible heat, which must occur before they 
can freeze. 

The theory of freezing mixtures has led to considerable 
improvements of their applications, and many new and 
curious discoveries have resulted in pursuing this inqui- 
ry. Indeed whatever tends to disclose the laws of nature, 
cannot ultimately fail of subjecting her more or less to 
the uses of life, and of manifesting more and more the wis- 
dom of the creator. 

Having established the above facts respecting the cause 
of fluidity, Dr. Black proceeded to the second part of his 
inquiry, relating to vaporisation, and pursued it with the 
same abilities and success.* Finding the thermometer to 

^ " When we beat a large quantity of a fluid in a vessel, in 
the ordinary manner, by setting it on a fire, we have an opportu- 
nity of observing some other phenomena which are very in- 



SJBCT. III.] THIRD DISSERTATIONo 65 

remain stationary at 212^ in boiling water, he conceived 
the process of ebullition to be in some respects analogous 
to that of liquefaction, and that the heat which did not 
raise the temperature of the water, entered into union with 
it, and became latent in the steam. If this were the case, 
it should be re-evolved during the condensation of steam ; 
and thus a method was devised of ascertaining its thermo- 
metrick quantity. Dr. Black's experiments on this sub- 
ject were very numerous. I shall allude to such as put 

structive. The fluid is gradually heated, and at last attains 
that temperature which it cannot pass without putting on the 
form of vapour. In these circumstances, we always observe, 
that it is thrown into the violent agitation which we call boil- 
ing. This agitation continues as long as we throw in more 
heat, or any of the fluid remains, and Vm violence is proportion^ 
al to the celerity with which the heat is supplied. 

"Another peculiarity attends this boiling of fluids, which, 
when first observed, was thought very surprising. However 
long and violently we boil a fluid, we cannot niake it in the 
least hotter than when it began to boil. The thermometer al- 
ways points at the same degree, namely, the vaporifick point 
of that fluid. Hence the vaporifick point of fluids is often call- 
ed their Boiling point. 

" When these facts and appearances were first observed, they 
seemed surprising, and difierent opinions were formed with re- 
spect to the causes upon which they depend. Some thought 
that this agitation was occasioned by that part of the heat, which 
was more than the water was capable of receiving, and which 
forced its way through, so as to occasion the agitation of boil- 
ing ; others, again, imagined, that the agitation proceeded from 
air, which water is known to contain, and which is now expelled 
by the heat. Neither of these accounts, however, is just or 
satisfactory ; the first is repugnant to all our ex[)erience in 
regard to heat : we have never observed it in the form of an 
expansive fluid like air : it pervades all bodies, and cannot be 
confined by any vessel, or any sort of matter; whereas, the 
elastick matter of boiling water, can be confined b> external 
pressure, as is evident in the experiments made with Papin's 
digester." 

This quotation from Black's Lectures, {Vo\. I. p. 153,) is in- 
serted to show the state of the argument respecting the pheno- 
mena of ebullition previous to his researches. 

9 



66 THIRD DISSERTATION. [sect. iii. 

the phenomenon in the clearest light, and are perfectly 
Tinconnected with hypothesis. 

He noted the time consumed for raising a certain quanti- 
ty of water to its boiling point, and then kept up the same 
heat till the whole was evaporated, and marked the time 
consumed by the process. It was thus easily computed 
what the temperature would have been, supposing the rise 
to have gone on above 212^ in the same ratio as below it. 
The water was originally at 50° ; it boiled in four minutes, 
and in twenty minutes was all evaporated. In four minutes, 
therefore, it had gained 162° for 50^+162=212; and in 
twenty minutes would have gained 162x5 = 810^; which 
may, therefore, be considered as the equivalent thermome- 
trick expression of the latent heat of the steam. Another 
good illustration of the absorption of heat in the production 
of steam, is furnished by heating water under compression. 
It may then be raised many degrees above its ordinary boil- 
ing point ; but, on removing the pressure, a portion of steam 
rushes out, and the remaining water has its teuiperature 
lowered to 212V 

Hence we learn, that the conversion of water into vapour 
is attended with a great loss of heat to the surrounding 
bodies ; and although the perceptible temperature of water 
and steam are identical, the latter contains heat equivalent 
to between 800 and 900^ of perceptible or thermometrick 
temperature. When steam is reconverted into water, this 
large quantity of heat is again given out ; and hence a small 
portion of steam is capable of heating a large body of water 
try its boiling point. The knowledge of this fact is of great 
economical importance ; and in breweries and other manu- 
factories, where large bodies of water are required to be 

^ See Black's Experiments, which prove the absorption of heat. 
Lectures, Vol. I. p. 157, &c. 



jECT.iii] THIRD DISSERTATION. 67 

boiled, the steam, instead of being suffered, as formerly, to 
pass off into the air, is conveyed by pipes into other vessels of 
water, which it heats during its condensation. In the same 
way, rooms and houses are warmed by the heat evolved dur- 
ing the condensation of steam, in iron or copper tubes 
which traverse the building, and the method is at once safe 
and effectual. 

It is in consequence of the latent heat of steam, that, in 
the process of distillation, we are obliged to present so large 
a surface for condensation ; and it is not difficult, by the 
help of a still, to calculate the latent heat of steam. If, 
for instance, one hundred gallons of water at 50® be mixed 
with one gallon at 212^ the temperature of the water will 
be raised above li®. If, by the common still-tub, one gallon 
of water be condensed from the state of steam by one hun- 
dred gallons of water at 50®, in that case the water will be 
raised IP, which is about 9J° more than in the former in- 
stance. Hence it appears, that the heat imparted to a hun- 
dred gallons of cold water by eight pounds of steam, would, 
if it could be condensed into one gallon of water, raise it to 
950®. 

The average of the various experiments, which have 
been made on this subject, warrants us in placing the la- 
tent heat of steam between 900^ and 1000^ 

These facts demonstrate that the condensation of vapour 
is always a heating process, and that its formation must 
equally be attended with the production of cold. 

' About the year 1774, it was observed by Dr. Cullen, 
that a thermometer moistened with spirit of wine or ether, 

* " The Chemistry of Stahl, as it was cultivated in Germany, 
and France, and other countries of Europe, scarcely aspired he^ 
yond the bounds within which it had been circumscribed by its 
original founder. A few important facts, indeed, were added, but 
they were either connected with medical preparations, or attract- 
ed attention solely as objects of curiosity. The great and tempt- 
ing field of Philosophical Chemistry lay unexplored, when it was 



'68 THIRD DISSERTATION. Isect.iii. 

sinks many degrees during the evaporation of those fluids ; 
with others, the thermometer may be made to fall from 60* 
toO^ The cause of this is sufficiently explained by Dr. 
Black's theory ; the ether and spirit readily pass into va- 
pour, which requires a certain quantity of heat for its pro- 
duction ; this is taken from the, bodies it happens to be in 
contact with, as from the thermometer or the hand ; hence 
the cold perceived when these fluids are applied to the 
body, and the advantage which results from their applica- 
tion in cases of burns, and inflammations. These circum- 
stances led Dr. Cullen to accelerate the evaporation of these 
fluids, by exposing them under the receiver of the air-pump ; 
by placing a flask half full of ether in a tumbler of water, 
it was found that, during the process of exhaustion, the eva- 
poration was so rapid from the ether in the flask, as to con- 
vert tbe surrounding water into iceJ 

entered upon with ardour by Dr. Cullen, who (irst perceived its 
value, and whose genius and industry, had they not been turned 
into another channel, would, in all probability, have been crown- 
ed with the richest discoveries. But though Dr. Cullen soon 
abandoned his chemical pursuits for those of medicine, he was 
fortunate enough to have initiated into the science, a man whose 
discoveries formed an era in chemistry, and who first struck out 
a new and brilliant path, which was afterwards fully laid open, 
and traversed with so much eclat by the British philosophers who 
followed his career. This fortunate pupil of Dr. Cullen, was Dr. 
Joseph Black." Thompson^ History of the Royal Society, p. 468. 

Dr. Cullen's fame as a promoter of chemistry has been lost in 
his greater celebrity as a teacher of medicine. " Chemistry," 
says his biographer, Dr. Anderson, " which was, before his time, 
a most disgusting pursuit, was, by him, rendered a study so pleas- 
ing, so easy, and so attractive, that it is now pursued by numbers 
as an agreeable recreation, who, but for the lights (hat were thrown 
upon it by Cullen and his pupils, would never have thought of 
engaging in it at all." 

Cullen was born in Lanarkshire, in 1712, and died at Edin- 
burgh in 1790. 

* Dr. Cullen's paper is published in the Physical and Literary 
Essays and Observations. Edinburgh, 1 756. Vol. II. It con- 



sicT.iii.] THIRD DISSERTATION. 60 

This part of the philosophy of heat, regarded in its con- 
nexion with the phenomena of nature, opens pleasing views 
of her order and economy. In the constant evaporation 
from the earth's surface, from rivers, lakes, and the sea, we 
discern an unfailing cause of equalization of heat ; the va- 
pour thus formed, ascending to colder regions, there be- 
comes a source of increase of temperature, and, re-assum- 
ing fluidity, is thrown upon the earth in fertilizing showers, 
or forming torrents among the mountains, and rivers in the 
valleys, is returned to the parent ocean, and again becomes 
active in a similar cycle of changes. 

But besides these obvious and complete changes in the 
state of matter connected with the evolution or absorption 
of heat, there are others in which similar alteration of tem- 
perature is observed, without a positive change of form. 

tains the details of many interesting experiments upon the pro- 
duction of cold, and he considers the power of fluids in this re- 
spect, as nearly according to the degree of volatility in each. 
*' If to this," says he, " we join the consideration that the cold is 
made greater by whatever hastens the evaporation, and particu 
larly that the sinking of the thermometer is greater, as the air in 
which the experiment is made is warmer, if dry at the same time, 
I think, we may now conclude, that tlu cold produced is the effect 
of evaporation,'^'' 

A very curious and ingenious method of accelerating the evapo- 
ration of water, so as to produce a freezing temperature, has late- 
Jy been devised by Professor Leslie. If we place a small basin 
of water under the receiver of the air-pump, its temperature will 
sink a few degrees during exhaustion. If a large surface of 
oil of vitriol be at the same time included in the exhausted re 
ceiver, the vapour of the water is rapidly absorbed by that fluids 
the perfection of the vacuum is thus maintained, the production 
of vapour is extremely rapid, and the quantity of heat absorbed 
for its formation so considerable, as to allow of the conversion of 
the remaining water into ice. Other absorbents, such as dry clay, 
oatmeal, (fee. may be substituted for the acid. The operation of 
wine and water coolers, and all cases in which diminution of tern- 
perature results from eva[)oration, are admiralilv explained upon 
Dr, Black's Theory of Latent Heat. 



70 THIRD DISSERTATION. [sect. m. 

Whenever the density of a body, whether solid, liquid, or 
aeriform, is varied, there is an equivalent variation in its la- 
tent heat. The speciBc gravity of soft iron is increased by 
hammering, and heat is evolved during the operation. A 
piece of Indian rubber, suddenly extended, becomes warm. 
If water be mixed with oil of vitriol, the density of the 
water is increased, and there is a very considerable aug- 
mentation of temperature. If air be suddenly compressed, 
it retains its elastick state, but becomes violently heated ; on 
the other hand, if air be quickly rarified, there is an equiva- 
lent reduction in its temperature. In these cases, bodies 
are said to change their capacities for heat ; increase of 
density is attended with a diminution of capacity for heat ; 
and diminution of density with an increased capacity. The 
phenomena thus presented are such as the doctrine of la- 
tent heat would lead us to expect. When a fluid is con- 
verted into a solid, there is a copious evolution of heat ; 
when a fluid approximates to a solid state, or where its den- 
sity is increased, we might expect that heat would also be 
evolved.^ 

The last train of investigation, in regard to heat, which 
occupied Dr. Black's thoughts, related to the different quan- 
tities of heat contained in different substances of the same 
temperature, without relation to change of density or state. 
A reference to an experiment will, perhaps, render this 
point more intelligible. If, for instance, a given quantity 
of boiling water, surrounded with ice, in sinking from 212® 
to 32® melts one pound of ice, and if the same quantity of 
olive oil, in passing from the same to the same temperature 
melts only half a pound of ice, we should conclude, that, 

^ The sinking of a thermometer suspended in the receiver of the 
air pump, during exhaustion, and its subsequent rise upon the 
readmission of air, are noticed by Dr. Cullen in the paper just 
|uoted. 



8KCT.III.] THIRD DISSERTATION. 71 

although the thermometrick temperature of the two fluids is 
similar, the actual quantity of heat contained in the water, 
and ascertainable by its effects upon the ice, is twice that 
contained in the oil. To signify the quantity of heat thus 
contained in different bodies of the same temperature, the 
term specijick heat has been employed — we thus should 
state, from the result of the experiment alluded to, the spe- 
cifick heat of water to be 2, that of the olive oil 1. Irvine, 
Crawfurd, Wilcke, Lavoisier, and several eminent Experi- 
mentalists of the present day, have engaged themselves in 
researches on this subject, but the inquiry originated with 
Dr. Black, in the year 1762. 

In these limited observations upon the discoveries of 
Black, I hope to have rendered myself intelligible upon 
those main points of his investigations, which constitute the 
foundation of some of the most important and refined doc- 
trines of chemical science. The distinct object of this dis- 
course being to record the march of chemical discovery, and 
not to unfold the principles of the science, it would be un- 
wise to indulge in more extended incursions upon this fertile 
ground, or to trace the great trunk of his researches to its 
extreme ramifications. But a partial glance at the facts dis- 
closed will show even a superficial observer, the obligations • 
we are under to the discoveries of this eminently modest 
and unassuming Philosopher. Of many of the most intri- 
cate phenomena of nature, they furnished new, easy, and 
luminous explanations ; and to the arts they were of un- 
paralleled benefit ; for, by developing their connexion, not 
with the shadows merely, but with the depths of science, a 
new road was opened to their improvement and perfection. 

Among the learned lookers-on of this period we discern 
many who, with independent and liberal minds, loved and 
patronized science for its own sake, and they were pleased 
at its rapid progress under the auspicious guidance of 



72 THIRD DISSERTATION, [sect, hi, 

Black. Others, actuated by motives illiberal and inte- 
rested, countenanced sciences solely upon the selfish prin- 
ciple of gain ; the puerile and short-sighted questions of 
cui bono was constantly on their lips; but even they have 
been silenced by the application of Black^s discoveries-^^ 

^ This may be the proper place to show in what way the 
views of Dr. Black's Theory of Latent Heat are connected with 
the improvements of the steam-engine — a subject upon which 
I must necessarily be brief, as only in part belonging to the ob- 
ject of this discourse. The Marquis of Worcester is commonly 
regarded as the inventor of the steam-engine, but his claims 
are not well authenticated. It is true, that, among the Utopian 
schemes to be found in his Century of Inventions, there is a 
dark description of a method of raising water by steam ; but 
we can scarcely see how this was effected, nor are there any 
data recorded of the success of the contrivance. Be this as it 
may, he who barely and obscurely hints the possibility of an 
undertaking cannot be regarded as forestalling him who success- 
fully carries it into execution ; and the first person, w ho, upon 
decided evidence, constructed an engine for raising water by the 
alternate force and condensation of steam, w^as Captain Savary, 
— who also published an account of his invention in a small 
tract called the Miner's Friend. To enter into a description of 
this instrument would be irrelative to my present purpose ; I 
therefore pass on to that of Nevvcomen, who, in 1 705, obtained 
a patent for an improved steam-engine. It consisted of a boiler 
having a cylinder placed upon it, in which was a solid plunger 
connected by its rod with a beam and lifting pump. The 
plunger was elevated by the elastick force of steam admitted 
from the boiler. The steam-cock being closed, a small stream 
of cold water w^as suffered to run into the cylinder, by which 
the steam was condensed ; the pressure of the atmosphere then 
acting upon the surface of the plunger, forced it to the bottom 
of the cylinder, whence it was again raised by the readmission 
of steam, and so on. In 1717, Mr. Henry Beighton became an 
improver of the steam-engine ; he was probably the first who 
caused the steam-cock to be opened and shut by the machine- 
ry, for a man was obliged to attend Newcomen's engine for 
this express purpose. A few other improvements were made by 
different persons, but they did not affect the general action of 
the engine ; the steam was alternately admitted into, and con- 
densed in the main cylinder; and although defects in its pow- 
er had been noticed, their cause was unknow^n until 1765, 



sBcr. IV.] THIRD DiSSERTATIONo 73 



SECTION IV. 

RESEARCHES RELATING TO THE COMPOSITION OF ATMOSPHERICK AIR. 
—EXPERIMENTS OF RUTHERFORD AND OF PRIESTLEY. 

Of the various discoveries, which it is the object of this 
Dissertation to unfold, none have been more important in 
their consequences than those relating to the composition 

i^vhen, happily for the prosperity of the arts and rtianufactures 
of this country, the subject engaged the keen ingenuity of Mr. 
Watt. The model of a Newcomen's engine fell into his hands 
to be repaired, and in this he presently observed the immense 
loss of steam occasioned by its admission into the cylinder just 
cooled for condensation ; indeed, he went so far as to ascer- 
tain, by experiment, that half the steam of the boiler was thus 
lost. For, haviog constructed a boiler which showed the 
quantity of steam expended at every stroke of the engine, he 
found that it many times exceeded that which was sufficient to 
fill the cylinder. But the circumstance that excited his great- 
est surprise was, that the injection water gained infinitely more 
heat than if a quantity of boiling water, equal to that required 
to form the steam, had been added to it. It was probably in 
this dilemma that he consulted Dr. Black — and the explanation 
of the difficulty will be obvious from the facts detailed in the 
text. To avail himself, therefore, of the whole power of the 
steam, it became absolutely necessary to keep up the tempera- 
ture of the cylinder constantly at the boiling point of water ; 
this he was enabled to attain, by connecting with it another 
vessel, exhausted of air, and immersed in cold water, into 
which, when communicated with the cylinder, the steam, being 
an elastick fluid, instantly rushes and is condensed, and, on 
closing its connexion with the cylinder, the steam, again ad- 
mitted there, now operates with full force, and suffers no further 
condensation. To carry off the water from this second vessel, 
which he calls the condenser, and to perpetuate the vacuum, 
Mr. Watt attached to it a pump by which both the air and con- 
densed water are removed. The engine thus altered produced 
the same power as one of equal dimensions on Newcomen's 
plan, with rather less than one-third the quantity of sfeam ; 
hence was a considerable hindrance to the use of the engine 

10 



74 THIRD DISSERTATION. [sect. iv. 

of atmospherick air, a subject which the ancients seem not 
to have thought upon, since they regarded it as an ele- 
ment, or ultimate principle of matter.' In this, as in most 
other branches of experimental science, the advances of 
the human mind have been verj gradual : Mayow, in 1674, 
was upon the very brink of that stream of discovery, 
which, in 1774, carried Priestley into the fastnesses of 
Pneuraatick Chemistry. Hales, by showing the mode of 
disengaging and collecting gaseous fluids, removed many 
of the most serious obstacles which encumbered this path 

materially diminished, namely, the expense of fuel. But great 
as was this improvement, it forms a small part of the 
successful achievements of Mr. Watt in this department 
of mechanicks; he amended the apparatus for boring the 
cylinders, and improved every part of the working gear of 
the engine; and he infinitely extended its applications and 
utility, by applying the power of steam to produce motion 
round an axis; but their enumeration would lead me out of the 
bounds of chemistry. 1, therefore, hasten to the invention 
which may be said to have perfected the steam-engine. Steam 
had hitherto only been used to force the piston down, — it was re- 
turned by a weight attached to the other end of the beam. Mr. 
Watt, in 1782, constructed an engine in which steam was used 
to elevate as well as to depress the piston, an alternate vacuum 
being formed above and below it, by the condenser, as before. 
An engine upon this plan, executed at Mr. Watt's manufactory at 
Soho, near Birmingham, was first employed at the Albion Mills in 
1788. 

An excellent sketch of the history of the steam-engine will 
be found in the Edinburgh Review, Vol. XIII. p. 311. 

' Thus Lucretius, — 

Aera nunc igitur dicara, quid corpore toto 
InnuQierabiliter privas inutatur in boras : 
Semper en-m, quodquomque tiuit de rebus, id omne 
Aeris in inagnum fertur mare, qui nisi contra 
Corpora retribuat rebus, recreetque fluenteis, 
Omnia jam resolula forenl. et in aera vorsa, 
Hand ig-tur ressat gigni de rebus, et in res 
Recidere assidue, quoniam fluere omnia constat. 

De Rerum Natura, Lib. V. v. 274 



5f.cT. iv] THIRD DISSERTATION. 75 

of research ; he was followed by Boerhaave, and after- 
wards by Black, who, having reached (he discovery of 
fixed air, turned into another road of investigation. Nei- 
ther Mayow, therefore, nor Hales, nor Boerhaave, nor 
Black, were very diligent cultivators of Pheuaiatick Chem- 
istry ; they had, indeed, opened the mine, but did not 
explore it; its treasures were reserved for those whose la- 
bours we are now about to recount, and were chiefly borne 
away by the diligent dexterity of Dr. Joseph Priestley. 

If we trust the quotations of Rey already cited, the 
necessity of air, in the process of combustion, was not 
only observed, but inquired into by Caesalpinus ^ and Li- 
bavius, ^ as far back as the sixteenth and early part of the 
seventeenth century. Mayow insisted that a part only of 
the atmosphere was concerned in the phenomena of com** 
bustion, and found that air, in which bodies had burned, 
became unfit for the respiration of animals.^ As soon as 

' Born at Arezzo in 1519 ; died at Rome in 1603. His medi- 
cal works contain some scattered chemical observations, which, 
however, are of little importance. 

^ Libavius has sometimes been cited as the most rational che- 
mical inquirer of his age, but of this character 1 can find no jus- 
tification in his writings upon chemical subjects ; they are 
either unintelligible, or trifling; he certainly had some merit as 
a contriver of apparatus, and his furnaces and distillatory ves- 
sels appear to have been ingeniously devised. 

He died in 1616. 

^ " Nempe animalculum quodvis una cum lucerna in vitro in- 
cludatur, ita ut aeri externo aditus praecludatur, quod facile fac- 
tu est. Quo facto lucernam istam brevi expirantem videbimus ; 
neque animalculum diu tedae ferali superstes erit. Etenim ob- 
servatione compertum habeo, animal una cum lucerna in vitro 
inclusum, baud multo plus, quam dimitlium temporis istius, quo 
alias viveret, spiraturum esse." Traclatus quhique, cap. vii. 
He then goes on to show that an animal requires less air than that 
wanted for the combustion of a candle, and endeavours to prove 



76 THIRD DISSERTATION. [sicr. iv. 

it had been ascertained that, in the phenomena of com= 
bustion and respiration, a portion of fixed air was generat- 
ed, the extinction of burning bodies, and the death of ani- 
mals immersed in air, thus rendered foul, were referred to 
the presence of that gaseous body, its noxious qualities 
having been amply proved by Black and others ; and this 
opinion seemed to be sanctioned by the discovery, that 
air thus tainted by respiration and combustion, might, in 
some measure, be restored to purity by exposure to the ac- 
tion of lime water, which absorbed the fixed air. 

In 1772, Dr. Rutherford, Professor of Botany in the 
University of Edinburgh, published a thesis on Fixed, or, 
as it was then called, Mephilick air, from which the follow- 
ing passage is extracted.' " By the respiration of ani- 
mals, healthy air is not merely rendered mephitick, but 
also sutfers another change. For, after the mephitick por- 
tion is absorbed by a caustick alcaline lixivium, the re- 
maining portion is not rendered salubrious, and although 

that the air in which an animal has been suffocated will not sup- 
port flame. " Verisimile est autem aerem, qui vitae sustinendae 
inidoneus est, etiam ad flammam conflandum ineptum esse.^ — 
Qnoniam ad lucernae deflagrationem majori particularum aerea- 
rura copia quam ad vitam sustinendam opus sit. Advertendum est 
autem hie loci, quod etsi flarama vitaque iisdem particulis sus- 
tinentur, non tamen propterea putandum est, sanguinis massam 
revera accensum esse. Tractatus quinquCy L. c. Mayow's ob- 
servations on the changes produced by the breathing of animals, 
on the air, are not less acute than those relating to the phenome- 
na of combustion. 

' " Sed aer salubris et purus, non modo respiratione animali 
ex parte (it mephiticus, sed et aliam indolis suae mutationem inde 
patitur. Postquam enim omnis aer mephiticus ex eo, ope lixivii 
caustici secrelus et abductus fuerit, qui tamen restat nullo modo 
galubrior inde evadit, nam quamvis nullara ex aqua calcis prae- 
cipitationem faciet, baud minus quam antea, flammam et vitam 
extinguit." 



ficT.iv] THIRD DISSERTATION, 77 

it occasions no precipitate in lime water, it nevertheless 
extinguishes flame, and destroys life.'* 

Thus we have traced the discovery of two gaseous 
jBuids differing from common air : fixed air, discovered by 
Black, and asotCj as it has since been called, by Ruther- 
ford. The former, a component part of chalk, and of the 
mild alcalis, the product of the combustion of charcoal, 
and of the respiration of animals ; the latter an ingredient 
of atmospherick air. 

It would be a wearisome and unprofitable occupation to 
record, even in brief terms, the transactions of a set of 
cavilling philosophists who started up in this country, and 
elsewhere, about the present period of our history ; their 
names have sunk into oblivion, and their works were only 
read while recommended by novelty. Some of them I 
have reluctantly perused, and have found that they are 
rather calculated to weary the attention than to satisfy cu- 
riosity, or impart information. 

I therefore hasten to one of the most remarkable and 
splendid epochs of chemical science, adorned by discove- 
ries which have been rarely equalled, either in number or 
importance, and ushered in by a series of sterling facts 
and memorable investigations. The well known names of 
Priestley, Scheele, Cavendish, and Lavoisier, now appear 
upon the stage, and it will be an arduous but gratifying 
task to follow them through their respective parts. In this 
recital, a strict adherence to the dates of discoveries 
would neither be convenient nor useful, and I shall rather 
therefore deviate a little on this point, than cloud the per- 
spicuity of my narrative, or cramp it by chronological 
strictness. 

Dr. Priestley's character was of so composite an order 
as to defy brief description or superficial delineation ; he 
was a politician, a divine, a metaphysician, and a philoso- 



78 THIRD DISSERTATION. [srct.iv. 

pher ; and in each of these callings he displayed abilities 
of a peculiar and occasionally exalted description. His 
copious and important contributions to chemical science 
are the more surprising, when it is remembered that his 
philosophical pursuits were merely resorted to as a relaxa- 
tion in his theological studies ; that his mind was under the 
constant agitation of controversy and dispute ; that he was 
too impatient for deep research, and too hasty for premedi- 
tated plans. But, with all these bars against him, he was a 
thriving wooer of science: he made more of his time than 
any person of whom I ever read or heard ; and possessed 
the happy and rare talent of passing from study to amuse- 
ment, and from amusement to study, without occasioning 
any retrogade movement in the train and connexion of his 
thoughts. 

There is another important feature in Dr. Priestley's cha- 
racter, which may tend to throw some light on his contro- 
versy with the French school : He possessed the strictest 
literary and scientifick honesty ; he makes frequent men- 
tion of his predecessors and contemporaries, and enume- 
rates the ideas which he borrowed from them, and the ex- 
periments they suggested, with more than necessary accu- 
racy and minuteness. His attachment to Chemistry seems 
to have been formed at Leeds,^ about the year 1768, and be- 

* Dr. Priestley was born at Fieldhead, near Leeds, in March, 
1733. In 1758, he went to Nantwicb in Cheshire, where he es- 
tablished a school, and was, for the first time, enabled to pur- 
chase some philosophical instruments, in the use of which he in- 
structed his scholars. In 1 761 , he removed to Warrington, whence 
he made regular annual visits to the metropolis, and became ac- 
quainted with Mr. Canton, Dr. Franklin, and Dr. Watson, who 
assisted him in collecting materials for his History of Electricity. 
In 1767, Dr. Priestlej went to Leeds, where his attention was 
especially directed to the doctrine of air, in consequence of re- 
siding near a public brewery, where he amused himself by ex- 
periments on the fixed air produced by fermentation. " When I 



SBCT. IV.] THIRD DISSERTATION. 79 

tween that period and the year 1772, he had added several 
new and highly important facts to the science, which are de- 
tailed in a long communication presented to (he Royal So- 
ciety in the spring of that year. It is here that he relates 
those researches respecting the influence of vegetation upon 
the atmosphere, which led to entirely new views of the 
physiology of plants, and which displayed, in a striking 
light, some of those masterly and beneficent adjustments of 
nature, by which the different members of the creation are 
made to minister to each other's wants, and thus preserve 
that eternal harmony which marks the natural world. 

As combustion and respiration were connected with the 
deterioration of air, it occurred to Dr. Priestley to ascer- 
tain how far the growth of vegetables might be productive 
of similar effects. 

" One might have imagined," says he, " that since com- 
mon air is necessary to vegetable as well as to animal life, 
both plants and animals would affect it in the same manner ; 
and I own I had that expectation, when I first put a sprig of 
mint into a glass jar, standing inverted in a vessel of water ; 
but when it had continued growing there for some months, 

removed from that house," says he (Memoirs of his own life, p. 61,) 
" I was under the necessity of making the fixed air for myself; 
and one experiment leading to another, as 1 have distinctly and 
faithfully noted in my various publications on the subject, I by 
degrees contrived a convenient apparatus for the purpose, but of 
the cheapest kind." Dr. Priestley's first publication on the sub- 
ject was in 1772, and related to the imfjreo^nation of water with 
fixed air, and the same year, in the month of March, his Observa- 
tions on different kinds ef Air, were read before the Roj^al Society, 
to which body he continued to communicate his other valuable 
researches. In 1794, he embarked for America, and took up his 
residence in Pennsylvania, where he died on the 6th of February 
1804. 

We have here omitted all allusions to his religious opinions and 
controversies, referring our readers to his Memoirs, and to his 
life iu the (kneral Bioifraphical Dictionoryj. 



80 THIRD DISSERTATION. [sect, iv 

I found that the air would neither extinguish a candle, nor 
was it at all inconvenient to a mouse which I put into it." 

In experiments of this kind, Dr. Priestley points out the 
necessity of often withdrawing the dead and dying leaves, 
lest, by their putrefaction, they should injure the air; he 
also hints at the noxious powers of some plants, especially 
the cabbage, of which he kept a leaf in a glass of air for 
one night only, and in the morning a candle would not burn 
in it.^ 

Dr. Priestley also extended his experiments to the influ- 
ence of plants upon air vitiated by animal respiration and 
by combustion, and found that they in general did not only 
not contaminate the air, but that they actually restored to 
purity that which had been rendered impure by flame and 
breathing ; and by showing that this change was effected by 
groundsel as perfectly as by mint, proved it independent of 

* At the beginning of the last summer, I confined, in equal 
portions of atmospherick air, as nearly as possible, equal surfaces 
of the leavesof spearmint, cabbage, mustard, bean, pea, and the 
vine. The plants were all thriving, and, during a great part of 
the day, were exposed to the sun. The bulk of the air, which 
was confined over water, was not altered either by the mint or 
vine leaves; the pea and bean leaves caused a slight diminution, 
but the air, in contact with the cabbage and mustard plant, was 
lessened by about one fifteenth and one sixteenth of its original 
bulk, and it extinguished a taper, which the others did not. The 
duration of each experiment was 48 hours. The average of the 
thermometer, during the period, was 52^ and of the barometer, 
29,5 inches. This is not the place to enter into any explanation 
of these facts, or to enlarge the account of them ; they prove, 
however, a corroboration of Priestley's assertion, that diffrrent 
vegetables act very differently on the air, and may be useful in 
adjusting some discordant results of later experimentalists. Home 
plants are much more gross feeders than others, and the nature of 
the soil in which they grow may often be, in some degree, judged 
of by their flavour. Those vegetables which are of a very quick 
and luxuriant growth, and readily susceptible of the influence of 
manures, afi*ect the atmosphere more than those whose growth is 
comparatively slow, and whose foliage is sparing. 



sicT. iv] THIRD DISSERTATION. 81 

the aromatick oil, to which some in their ignorance had been 
willing to refer it. 

That actual vegetation was necessary, and the mere 
vegetable insufficient, he proved by exposing the pulled 
leaves of a mint plant to air, which were unproductive of 
the regeneration effected by the growing sprig. 

Dr. Priestley concluded from these experiments, that 
the noxious air resulting from combustion, and from the 
breathing of the different animal tribes, formed part of the 
nourishment of plants ; and that the purity of our at- 
mosphere, and its fitness for respiration, were materially 
dependent upon the functions of growing vegetables. 

Mayow in 1674, and Hales in 1724, had observed the 
production of gaseous matter during the action of nitrick 
acid upon the metals. I have before alluded to the very 
rude manner in which Mayow collected it. Hales ascer- 
tained its singular property of producing red fumes when 
mixed with common air. Dr. Priestley resumed these in- 
quiries, and pursued them with clever activity : he found, 
that, on mixing one hundred parts, by measure, of com- 
mon air, with one hundred of the air procured by the ac- 
tion of nitrous acid on copper, which he called nitrous 
gas, red fumes were produced, and there was a diminution 
of bulk equal to ninety -two parts in the two hundred ; so 
that one hundred and eight parts only remained. 

When fixed air was thus mixed with nitrous air, there 
was no diminution ; when air, contaminated by combustion 
or respiration, was used, the diminution was less than with 
purer air; and with air taken from different situations, 
Dr. Priestley thought he obtained rather variable results. 
Hence the beautiful application of nitrous air to the dis- 
covery of the fitness of other species of air, for combus- 
tion and respiration. 

n 



82 THIRD DISSERTATION. [sect, i^ 

It was for these discoveries that the Council of the 
Royal Society honoured Dr. Priestley by the presenta- 
tion of Sir Godfrey Copley's medal, on the 30th of No- 
vember, 1773.^ 

' " Sir Godfrey Copley originally bequeathed five guineas to 
be given at each anniversary meeting of the Royal Society, 
by the determination of the president and council, to the person 
Avho had been the author of the best paper of experimental ob- 
servation for the year past. In process of time, this pecuniary 
reward, which could never be an important consideration to a 
man of enlarged and philosophical mind, however narrow his 
circumstances might be, was changed into the more liberal form 
of a gold medal, in which form it is become a truly honourable 
mark of distinction, and a just and laudable object of ambition. 
It was, no doubt, always usual with the Presidents, on the de- 
livery of the medal, to pay some compliment to the gentleman 
on whom it was bestowed, but the custom of making a set 
speech on the occasion, and of entering into the history of 
that part of philosophy to which the experiment related, was 
first introduced by Mr. Martin Folkes. The discourses, how- 
ever, which he and his successors delivered, were very short, 
and were only inserted in the minute books of the Society; 
none of them had ever been printed before Sir John Pringle 
was raised to the chair of the Society." Chalmer's Biographi- 
cal Dictionary. — Life of Pringle. 

Dr. Franklin, in a letter upon the subject of this discovery 
to Dr. Priestley, has expressed himself as follows: 

*' That the vegetable creation should restore the air which 
is spoiled by the animal part of it, looks like a rational sys- 
tem, and seems to be of a piece with the rest. Thus, fire 
purifies water all the world over. It purifies it by distillation 
when it raises it in vapours, and lets it fall in rain; and farther 
still by filtration, when, keeping it fluid, it suffers that rain to 
percolate the earth. We knew before that putrid animal sub- 
stances were converted into sweet vegetables when mixed with 
the earth and applied as manure; and now, it seems that the 
same putrid substances, mixed with the air, have a similar ef- 
fect. The strong thriving state of your mint in putrid air, 
seems to show that the air is mended by taking something from 
it, and not by adding to it. 1 hope this will give some check 
to the rage of destroying trees that grow near houses, which 
has accompanied our late improvements in gardening, from an 
opinion of their being unwholesome. I am certain, from long 



8BCT. IV.] THIRD DISSERTATION. 83 

Sir John Pringle, who was then President, delivered, 
on this occasion, an elaborate and elegant discourse upon 
the different kinds of air, in which, after expatiating upon 
the discoveries of his predecessors, he points out the 
especial merits of Priestley's investigations : In allusion 
to the purification of a tainted atmosphere by the growth 
of plants, the President has thus expressed himself: 

" From these discoveries we are assured, that no vege- 
table grows in vain ; but that, from the oak of the forest 
to the grass of the field, every individual plant is service- 
able to mankind; if not always distinguished by some 
private virtue, yet making a part of the whole which 

observation, that there U nothing unheallby in the air of woods ; 
for we Americans have every where our country habilatioiis in 
the midst of woods, and no people on earth enjoy better health, 
or are more prolifick." Phil. Trans. 1772, page 199. 

Notwithstanding these researches, which have ex})0sed some 
very curious facts relative to the chemical physiology of plants, 
it must be confessed that the causes of the renovatiou and 
equality of our atmosphere are yet by no means ascertained ; 
for, although some growing vegetables do, under certain circum- 
stances, purify the air, (by the absorption of carbon and the 
evolution of oxygen,) yet, v,hen in a state of decay, the}' inva- 
riably add to its contamination, and a general view of the sub- 
ject would induce us to conclude, that tiiey do as uiuch harm 
as good, at least, if recent experiments connected with this sub- 
ject are to be considered as correct. 

These are the prominent features of Dr. Priestley's first com- 
munication to the Royal Society resj)ecting the different kiiiils 
of air, and had he bestowed no other contril)iaion upon chemis- 
try, the facts here detailed would have entitled him to a con- 
spicuous place among the benefactors of the science. The pa- 
per is divided into several sections, in which he discusses the 
nature an<l properties of fixed air; of the air contaminated by 
the combustion of candles and of brimstone; of if^Hammable 
air; of air infected wiih animal respiration or putrefaction ^ of 
air exjmsed to the action of mixtures of iron tilin2;s and sul- 
phur; of nitrous air ; of air in which metals have !u pti calcined, 
and which h;is been exposed to tiie action of white-lead paint ^ 
and of air procured by spirit of salt 



84 THIRD DISSERTATION. [sect. iv. 

cleanses and purifies our atmosphere. In this the fragrant 
rose and deadly nightshade co-operate ; nor is the herbage 
nor the woods that flourish in the most remote and un- 
peopled regions unprofitable to us, nor we to them, con- 
sidering how constantly the winds convey to them our 
vitiated air, for our relief and for their nourishment. And 
if ever these salutary gales rise to storms and hurricanes, 
let us still trace and revere the ways of a beneficent Be- 
ing, who not fortuitously, but with design, not in wrath, 
but in mercy, thus shakes the water and the air together, 
to bury in the deep those putrid and pestilential effluvia 
which the vegetables on the face of the earth bad been 
insufficient to consume." 

Such were Dr. Priestley's researches, and such the 
views to which he had been led previous to the year 
1773, when he undertook the examination of the air which 
rises from red lead, and from red precipitate of quick- 
silver, when those substances are exposed to heat. This, 
indeed, was one of the topicks upon which Hales had 
touched before him, but it was passed over with that 
hasty and! superficial carelessness of which his experimen- 
tal proceeding furnish so many instances, and in which 
he so often lost the substance by grasping at the shadow. 

Dr. Priestley cast his keenest eye upon the prospect 
now before him, and as the various objects came into 
view, he followed them up with more than his ordinary 
diligence and usual sagacity. The track he had entered 
upon was, indeed, of such abundant promise, as would 
have insnared the attention and excited the curiosity of 
one less awake than our author to its interest and novel- 
ty. But he, already well initiated in the management of 
aeriform fluids, proceeded with a rapidity which left his 
associates far behind, and carried him, in proud and un- 
disputed precedence, to the goal of discovery. 



UECT. iv.l THIRD DISSERTATION. 85 

The 1st of August 1774 is a red-letter day in the annals 
of Chemical Philosophy, for it was then that Dr. Priest^ 
ley discovered dephlogisticated air. Some, sporting in 
the sunshine of rhetorick, have called this the birth-day of 
Pneumatick Chemistry ; but it was even a more marked 
and memorable period ; it was then (to pursue the meta 
phor) that this branch of the science, having eked out a 
sickly and infirm infancy in the ill-managed nursery of the 
early Chemists, began to display symptoms of an impro- 
ving constitution, and to exhibit the most hopeful and un- 
expected marks of future importance. 

Dr. Priestley's original opinion, that all kinds of facti- 
tious air were noxious, seems first to have been shaken by 
observing that a candle would burn in air procured by 
distilling nitre in a gun barrel ; but the first experiment, 
which led to a very satisfactory result, was conducted as 
follows. A glass jar was filled with quicksilver, and in- 
verted in a basin of the same ; some red precipitate of 
quicksilver was then introduced, and floated upon the 
quicksilver in the jar ; heat was applied to it in this situa- 
tion by a burning lens, and " I presently found that air was 
expelled from it very readily. Having got about three or 
four times as much as the bulk of my materials, I ad- 
mitted water into it, and found that it was not imbibed 
by it. But what surprised me more than I can well 
express, was, that a candle burned in this air with a re- 
markable vigorous flame, very much like that enlarged 
flame with which a candle burns in nitrous air exposed to 
iron or liver of sulphur; but, as I had got nothing like 
this remarkable appearance from any kind of air besides 
this peculiar modification of nitrous air, and I knew no 
nitrous acid was used in the preparation of mercurius 



86 THIRD DISSERTATION. [sect, iv, 

calcinalus, I was utterly at a loss .^ how to account for 
it." ' 

He afterwards obtained the same kind of air by expos- 
ing red lead and several other substances to heat, and 
made a number of well-devised experiments upon its pro- 
perties. 

Those who, for the first time, witness the effect of this 
air upon burning bodies, will best picture to themselves 
the emotion and surprise of its discoverer, when he plung- 
ed a burning taper into it. The splendour of the flame 
was magnificently increased, the consumption of the wax 
was extremely rapid, and the heat evolved much more 
considerable than in common air. He found, in short, 
that, in all cases of combustion, the process was infinitely 
more rapid and perfect in this kind of air, than in the ordi- 
nary atmosphere;^ and he was thence induced to apply 
the term dephlogisticated to the gas he had thus obtained. 
He regarded it as air deprived of phlogiston, and thus ac- 
counted for its eager attraction for that principle which, 
during combustion, bodies were imagined to throw off. 

^ Experiments and Observations on Different Kinds of Air^ &c. 
Vol. II. p. 107. Birmingham, 1790. 

^ The following paragraph, with which Dr. Priestley prefaces 
iiis account of the discovery of dephlogisticated air, presents a 
picture of his mind in regard to the origin of his own re- 
searches. 

" The contents of this section will furnish a very striking il- 
lustration of the truth of a remark which I have more than once 
made in my philosophical writings, and which can hardly be too 
often repeated, as it tends greatly to encourage philosophical 
investigations; viz. that more is owing to what we cal! chance^ 
that is, philosophically speaking, to the observation of events 
arising from unknown causes, than to any proper design or pre- 
conceived theory in this business. This does not appear in the 
vrorks of those who write synthetically upon these subjects, but 
would, I doubt not, appear very strikingly in those who are the 
most celebrated for their philosophical acumen, did they write 
analytically and ingenuously." {Exp. andObs. Vol. II. p. 103.) 



SECT. IV.] THIRD DISSERTATION. 87 

On the contrary, he accounted for the extinction of flame 
by the air discovered by Rutherford, and since termed 
azote ^ or nitrogen,^ upon the idea that that aeriform fluid 
was charged or saturated with phlogiston, and he there- 
fore called it phlogisticated air.^ 

In enumerating the higher merits of Dr. Priestley as a 
discoverer, we must not forget the minor advantages which 
his ingenuity bestowed upon experimental Chemistry. — He 
supplied the Laboratory with many new and useful articles 
of apparatus, and the improved methods of managing, col- 
lecting, and examining gaseous fluids, were chiefly the re- 
sults of his experience. He was the first who, with any 
chance of accuracy, endeavoured to ascertain the relative 
or specifick gravities of the different kinds of air then 
known ; he observed that dephlogisticated air was rather 
heavier, and phlogisticated air somewhat lighter, than that 
of the atmosphere; nitrous air he conceived to be nearly 
of the same specifick gravity. His experiments were made 
by the help of a delicate balance and exhausted flask. 

The influence upon the respiration of animals of a spe- 
cies of air marked by the eminent perfection with which 
it supports combustion, did not escape Dr. Priestley's no- 
tice. On applying to it his test of nitrous air, he found 
the absorption produced on mixture greater than with at- 
mospherick air ; whence he conjectured its superiour fit- 
ness for the support of life ; he introduced mice into it, 
and found that they lived longer than in an equal bulk of 
atmospherick air ; he then had the curiosity to taste the 

* From a and ^6/>i, " destructive of life." 

' t. €, Producer of nitrick acid. 

^ The application of de{)hlogisticated air to obtain intense de- 
grees of heat, and its probat>le uses in medicine, were subjects 
which did not altogether escape Dr. Priestley's attention, and 
he has alluded to them in the section of the work already quo* 
ed, relating to its " Properties and uses." 



88 THJRD DISSERTATION. 



liECf. IV, 



gas himself, and after two or three respirations, he felt, 
or fancied he felt, a peculiar sensation of lightness and 
ease of the chest. ^^ Who can tell,'' says he, " but that 
in time this pure air may become a fashionable article in 
luxury. — Hitherto only two mice and myself have had 
the privilege of breathing it." To this he foolishly adds, 
that " the air which nature has provided for us is as good 
as we deserve.'' 

We have not yet exhausted Dr. Priestley's discoveries, 
but have seen enough to establish his claims to the title of a 
great benefactor to chemical science. If we compare him 
with his predecessor Black, he falls short in depth of 
judgment, but in quickness of conception, and industry of 
pursuit, he excels even such a standard of comparison. 
The one climbed the hill of discovery with slow and cau- 
tious steps, and calmly enjoyed the surrounding views ; 
the other made a more rapid ascent, but was giddy when 
he reached the summit ; hence those distortions and mis- 
conceptions, those erroneous notions and hasty conclusions 
which he who turns over the philosophical writings of Dr. 
Priestley cannot fail to discern. 

Upon the other productions of his pen, metaphysical, 
political, and moral, it is neither my province nor inclina- 
tion to dwell ; they abound in the defects, but are deficient 
in the merits, of his tracts upon chemical subjects.^ 

From the commencement to the termination of his busy 
career. Dr. Priestley was a staunch supporter of the unintel- 
ligible system of phlogiston ; he adopted it in all its ori- 
ginal incoherence and absurdity ; and the last of his sci- 
entifick publications was a tract in its defence, in which are 
adduced a variety of objections to the revived hypotheses 

[* It is much to be regretted, that the ingenious author should 
hazard this sweeping censure — a censure altogether out of place, 
and, as many will think, not less unfounded than impertinent.] 



SECT. IV.] THIRD DISSERTATION. 89 

of Rey and Mayow, and Hooke, which having long Iain 
dormant, were at this time erupted into the chemical world 
under the specious title of the French theory.' 

It will not be denied that the leading facts just detailed 
threw considerable light upon the nature and properties of 
atmospherick air; but those who have entitled Dr. Priest- 
ley the discoverer of its composition, have somewhat over- 
stepped the bounds of correctness. 

He seems, indeed, to have possessed no just notions 
of the difference between phlogisticated anddephlogisticat- 
ed air ; and, instead of regarding them as distinct chemi- 

' The tract alluded to in the text was published by Dr. Priest- 
ley after his retirement to America in 1800. It is entitled, The 
Doctrine of Phlogiston established, and that of the Composition of 
Water refuted. It contains a variety of miscellaneous observa- 
tions on the phlogistick and antiphlogistick theories, but it 
would be useless to follow the author into his unsubstantial 
speculations on these subjects. He has, however, thrown out 
some important considerations relating to his claims of originali- 
ty as the discoverer of dcphlogisticated air. The following 
paragraph appears of sufficient importance to be transcribed. 
" Now that I am on the subject of the right to discoveries, I 
will, as the Spaniards say, leave no ink of this kind in my ink- 
horn ; hoping it will be the last time that I shall have any oc- 
casion to trouble the publick about it." M. Lavoisier says {Ele- 
ments of Chemistry, English translation, p. 36,) " this species of 
air (meaning dephlogisticated) was discovered almost at the same 
time by Mr. Priestley, Mr. Scheele, and myself." The case 
was this : — Having made the discovery some time before I was 
in Paris in 1774, I mentioned it at the table of M. Lavoisier, 
when most of the philosophical people in the city were present ; 
aaying, that it was a kind of air in which a candle burned much 
better than in common air, but I had not then given it any name. 
At this all the company, and M. and Madame Lavoisier as 
much as any, expressed great surprise; 1 told them I had 
gotten it from precipitate per se, and also from red lead. Speak- 
ing French very imperfectly, and being little acquainted with 
the terms of chemistry, I said plomb rouge, which was not un- 
derstood, till M. Macquer said, I must mean minium, Mr. 
Scheele's discovery was certain independent of mine, though 
I believe not made quite so early." P. 88. 

12 



90 THIRD DISSERTATION. [sicx. it 

cal principles, adopted the notion of one elementary sub- 
stance, charged, in the one instance, with the imaginary es- 
sence of inflamaiability, and free from it in the other. In 
these inquiries, he frequently verges upon more correct 
and refined views, but has no sooner entered the right path, 
than phlogiston, like an ignis fatims, dances before his 
eyes, and leads him into the marshy mazes of errour. 

In the preceding investigations, Priestley followed 
those methods of collecting aeriform fluids over water, 
which Hales and others had employed before him : he now 
ascertained that there were some gases absorbed by or 
soluble in water. Mr. Cavendish, one of the most eminent 
Philosophers of that day, had announced this circumstance, 
and was puzzled by it ; but Dr. Priestley, with his usual 
and dexterous ingenuity, overcame the difliculty, by em- 
ploying quicksilver instead of water, over which fluid 
metal he preserved and examined several kinds of air, 
which are instantly deprived of their elastick state by the 
contact of water. 

The first permanently elastick fluid of this description 
which he examined, was the muriatick acid ; he obtained it 
by heating copper in the fluid acid, or common spirit of 
salt, and called it marine acid air. 

He immediately ascertained its absorption by water, and 
its powerful acidity ; he found it in(*apable of supporting 
flame, and extremely destructive of animal life. He ex- 
amined the action of a variety of substances upon this gas, 
and ascertained the remarkable rapidity with which it is 
absorbed by charcoal, and several vegetable and animal 
substances. Some unsuccessful attempts were made to 
ascertain the specifick gravity of this gas, from which 
Priestley correctly concluded, however, that it was a little 
heavier than air. 
This success attending these;experiments,andthe readiness 
with which he procured and retained the gaseous muriatick 



sKcr. IV.] THIRD DISSERTATION. 91 

acid, led him to extend his trials to other acids, when he found 
that, by acting upon vitriolick acid by inflammable substan- 
ces, he could procure from it a permanently elastick fluid, 
to which he gave the name of vitriolick acid air ; he found 
that, like the marine acid air, it was rapidly absorbed by 
water, and must be collected and preserved over quicksil- 
ver ; that it was nearly twice as heavy as atmospherick 
air ; that it extinguished flame, and was instantly fatal to 
animal life ; that it reddened vegetable blues, and destroy- 
ed most colours. This air is, in fact, produced by burn- 
ing sulphur in the atmosphere, and straw, wool, and other 
materials, are frequently bleached by exposing them to its 
fumes. ^ 

' Having elsewhere praised Dr. Priestley's candour, I insert 
the following extract from his history of the discovery of VitriO' 
lick Acid Air, to show the exactness with which he acknow- 
ledges the hints and assistance of others : 

*' My first scheme was to endeavour to get the vitriolick acid 
in the form of air, thinking that it would probably be easy to 
confine it by quicksilver, for, as to the nitrous acid, its affinity 
with quicksilver is so great that I despaired of being able to 
confine it to any purpose. I, therefore, wrote to my friend Mr. 
Lane to procure me a quantity of volatile vitriolick acid," &:c. 
" Seeing Mr. Lane the winter following, he told me, that if I 
would only heat any oily or greasy matter with oil of vitriol, 
I should certainly make it the very thing I wanted, viz. the 
volatile or sulphureous vitriolick acid ; and, accordingly, I 
meant to have proceeded upon this hint, but was prevented 
from pursuing it by a variety of engagements. 

'' Some time after this I was in company with Lord Shel- 
burne, at the seat of Mons. Trudaine, at Montigny, in France; 
where, with that generous and liberal spirit by which that no- 
bleman is distinguished, he has a com[)lete apparatus of [)hilo- 
sophical instruments, with every other convenience and assist- 
ance for pursuing such philosophical inquiries as any of his nu- 
merous guests shall choose to entertain themselves with. In 
this agreeable retreat I met with that eminent philosoj)her and 
chemist, Mons. Montigni, Member of the Royal Academy of 
Sciences: and conversing with him upon this subject, he pro- 



92 THIRD DISSERTATION. [buct. iv. 

Having thus obtained permanent aeriform fluids, having 
acid qualities, it occurred to Dr. Priestlej, that the vola- 
tile alcali, the substance which gives pungency to salvola- 
tile, spirit of hartshorn, and similar compounds, might be 
also procured in a pure and isolated gaseous form ; and, 
after several unsuccessful trials, he succeeded, by heating 
a mixture of quicklime and sal ammoniack, when a great 
quantity of air escaped, permanent over quicksilver, but, 
like the acid gases, rapidly absorbed by water. 

The odour of this gas was pungent in the extreme, and 
it possessed the property of salvolatile, smelling salts, and 
similar substances, of turning vegetable blues to green. 
After several experiments, in which the absorbing powers 
of different substances in regard to this air, were tried, Dr. 
Priestley became impatient to discover the effect of mixing 
it with the acid airs just described, — he imagined that he 
should form a neutral air. On putting this notion, however, 
to the proof of experiment, he was surprised to observe 
that when marine acid air, and the volatile alcaline air, 
were mixed in due proportions, they were wholly con- 
densed into a solid. And with sulphureous air a very simi- 
lar result was afforded* 

Dr. Priestley concluded that alcaline air was considera- 
bly lighter than acid air, because, on mixing them over 
mercury, he observed the former to float above the latter ; 

posed our trying to convert oil of vitriol into vapour, by boiling 
it on a pan of charcoal in a cracked phial. This scheme not 
answering our purpose, he next proposed heating it together 
with oil of turpentine. Accordingly, we went to work upon it, 
and soon produced some kind of air confined with quicksilver; 
but our recipient being overturned by the suddenness of the 
production of the air, we were not able to catch any more than 
the first produce, which was little else than the common air which 
had lodged on the surface of the liquor, and which appeared to 
be a little phlogisticated, by its not being much affected by a 
mixture of nitrous air." 



saCT.iv] THIRD DISSERTATION. 93 

on putting'a lighted candle into alcaline air the flame was 
enlarged, and a portion of the air appeared to burn with 
flame. 

We have now considered the principal discoveries of 
Dr. Priestley, upon which his title to originality rests, and it 
must be allowed that they are not less important than nu- 
merous. If we even consider them merely as insulated 
facts, they are of a very superiour character, and tended 
greatly to enlarge our knowledge of the chemical elements 
of matter ; but the new views of many natural and artifi- 
cial phenomena, which they exposed, and which before 
were buried in deep obscurity, confer upon them a more ex- 
alted aspect, and have obtained for them the deserved meed 
of universal admiration. In perusing Dr. Priestley's tracts, 
we find the thread of the narrative occasionally knotted 
with conceit, and weakened by garrulity; but these blemishes 
are compensated by prevailing candour and perspicuity of 
style : he had greatly extended the boundaries of science, 
and was awake to the importance of his conquests ; but re- 
sisted that febrile thirst of innovation and reform, which 
was endemick among contemporary Chemisls. 

" At present," says he, in the Preface to his third vo- 
lume of Experiments and Observations^ relating to various 
branches of Natural Philosophy, " At present all our sys- 
tems are in a remarkable manner unhinged by the discovery 
of a multiplicity of facts ^ to which it appears difficult or 
impossible to adjust them : We need not, however, give 
ourselves much concern on this account. For when a suffi- 
cient number of new facts shall be discovered, towards 
which even imperfect hypotheses will contribute, a more 
general theory will soon present itself, and perhaps to the 
most incurious and least sagacious eye. Thus, when able 
navigators have, with great labour and judgment, steered 
towards an undiscovered country, a common sailor, placed at 



94 THIRD DISSERTATION. [ssct. v, 

the mast head, may happen to get the first sight of land. Let 
us not, however, contend about merit, but let us all be intent 
on forwarding the common enterprise, and equally enjoy any 
progress we may make towards succeeding in it, and, above 
all, let us acknowledge the guidance of that great Being, 
who has put a spirit in man, and whose inspiration giveth 
him understanding." With this quotation, sufficiently cha- 
racteristick of his general style, I shall take leave of Dr. 
' Priestley, and introduce another hero of chemical history, 
his contemporary and great rival, Scheele. 



SECTION V. 

DISCOVERIES OF SCHEELE AND CAVENDISH. 

Among those whose names became eminent in the history 
of chemical science during the first half of the eighteenth 
century, Margraaf and Bergman are entitled to particular 
mention. The former was a pupil of the once celebrated 
Neumann,^ a man whose works are now not much thought 

* Casper Neumann was born at Zullichau in Prussia, in 1682, 
and in 1705 we find him enjoying the patronage of the King of 
Prussia, by whom he was sent to complete his studies at the Uni- 
versity of Halle. In 1711, he became a pupil of Boerhaave, and 
shortly after visited England, whence he accompanied George I. 
to Hanover, in 1716. In 1723 he became Professor of Practical 
Chemistry in the Royal College of Berlin, where he died in 1 737. 
His works consist chiefly in dissertations on various subjects of 
chemical inquiry, published in the Transactions of the Royal So- 
ciety^ and in the Miscellanea BeroUnensia, His Lectures were 
not printed till after his death, and proved a valuable maga- 
zine of chemical knowledge. " The author," says Dr. Lewis, 
who edited his works, " biassed by no theory, and attached to no 
opinions has inquired by experiment into the proportions and 
uses of the most considerable natural and artificial productions, 
and the preparations of the principal commodities which depend 



SECT, v.] THIRD DISSERTATION. 95 

of, but who did considerable service to the Chemistry of 
his day, and was evidently possessed of great diligence and 
some capacity. In 1733, Margraaf pursued chemistry un- 
der Juncker at Halle, and, having returned to Berlin in 
1738, we find several of his contributions in the Transac- 
tions of the Scientijick Society of that capital. Subsequent 
to that period, his works were collected and published at 
Paris in 176'2. They contain a great body of information, 
at that time novel and important, but they are chiefly en- 
titled to notice as furnishing specimens of the art of analysis, 
which was afterwards carried to greater perfection by Berg- 
man,^ who, indeed, may be considered as the first who point- 
ed out the true objects of that branch of the science, and 
who aimed at conferring upon it the statical accuracy which 
has since rendered it so important and useful. 

But Bergman was something more than a diligent experi- 
mentalist and acute reasoner ; he was also an active patron 
of science, and had the merit of rescuing Scheele from his 
obscure situation, and of discerning that talent and genius 
in the bud, which was afterwards so vigorously fruitful. 

If we compare Scheele with our own countrymen, we 
discern him possessed of the accuracy and cool judgment 
of Black, conjoined with the inquisitive and busy activity 
of Priestley, and his success in the pursuit of science was 

on chemistry; and seems to have candidly, and without reserve, 
communicated all he discovered." 

' Born at Berlin in 1709, where he died in 1782. 

' Torbern Bergman was born in Sweden in 1735, and died iu 
1784. His principal chemical papers are contained in the Opus- 
CT/Za, published at Upsal in 1779. They contain much to ad- 
mire, not merely as being ricb in facts and di^jcoveries, but also 
on account of the general view which he takes of the mode of 
prosecuting philosophical incjuiry, and which is so ably set forth 
in the preliminary essay, Dc lnda<^ando Vcro. The Opuscula. 
was translated into English by Dr. Edmund Cullen in 1788. 



96 THIRD DISSERTATION. [srct. v, 

such as might be expected to flow from this happy and 
rare union of opposite talents. In the number of his dis- 
coveries, their weight, and novelty, he has indeed very 
few equals ; nor has their splendour been tarnished by 
time, or dimmed by the brilliant light of modern investi- 
gation. 

Scheele is among the fortunate few, who, starting from 
an obscure original, have attained the zenith of scientifick 
eminence. He was born in 1742 at Stralsund, where his 
father was a tradesman. His youthful days were passed 
in the house of an Apothecary at Gottenburgh, where, by 
singular perseverance, and that kind of industry which is 
prompted by strong natural inclination, he acquired a 
valuable stock of chemical information. In 1773, having 
removed to Upsal, accident brought him acquainted with 
Bergman, who became his friend and patron, and to whose 
honour be it told, that when Scheele's reputation after- 
wards rose to such a height as threatened to eclipse his 
own, instead of listening to the voice of jealousy, which, 
on such occasions, is too common a frailty, he became 
more zealous in behalf of his rival, and more indefatigable 
in the service of his friend. Scheele afterwards removed 
to Koping, in the neighbourhood of Stockholm, where he 
died in 1786. 

No adventitious aid, however, can be said to have con- 
tributed to Scheele's greatness. On the contrary, obsta- 
cles were opposed to his progress which would have damp- 
ed the ardour, and checked the flight, of less aspiring and 
persevering minds ; and much of his useful life was spent, 
'^ not in the soft obscurities of retirement, or under the 
shelter of academick bowers, but amid inconvenience and 
distraction, in sickness and in sorrow." 



sBCf.v] THIRD DISSERTATION. 97 

Scheele's first publication, which appeared in the Stock- 
holm Memoirs^ for the year 1771, relates to the analysis 
of fluor spar. The peculiarities of this substance were 
first noticed in 1768 by Margraaf, but the discovery of 
the principle upon which they depend was reserved for 
the superiour sagacity of Scheele, who demonstrated in it 
the existence of lirae, and acid till then unknown, which 
he called fluorick acid. Scheele had applied acid of vi- 
triol with great success to the analysis of a variety of sub- 
stances, and on exposing powdered fluor spar to its action 
in a glass retort, he obtained the new body in question. 
The fluorick is one of the few acids w^hich rapidly cor- 
rode glass; it dissolves silicious earth, a component part 
of glass ; and forms with it in an aeriform compound, per- 
manent until it touches water, when part of the silicious 
earth is deposited. Scheele, not aware of this fact, at first 
conceived that silicious earth was a compound of fluorick 
acid and water, for, on evolving the gas in a glass retort, 
and allowing it to pass into water, every bubble was coated 
with a film of flint; but he afterwards learned, that it was 
derived from the retort, which is soon eaten into holes. It 
is this property of fluorick acid which has led to its em- 
ployment for the purpose of etching upon glass. 

Scheele was next occupied in a series of researches on 
manganese, a mineral substance abundant in many parts of 
the world, but of which the nature was unknovvn until the 
appearance of his Disseriaiion upon it in 1774. This 
tract is full of important facts, and glitters with brilliant 
discoveries. We are here first informed that manganese is 
a metallick calx ; that in its crude state it often contains a 
peculiar earth, to which the name baryies has since been 

* Scheele's Essays have been collected an<l translated into 
English by Dr. Thomas Beddoes. London, 1786. 

13 



98 THIRD DISSERTATION. [sect. y. 

applied ; that the volatile alcali contains nitrogen as one 
of its essential component parts. But the most remarka- 
ble novelty announced in this Essay, is the discovery of a 
peculiar gaseous fluid of a yellow colour, which Scheele 
considered as the basis of the rauriatick acid ; conceiving 
the addition of phlogiston requisite to the restoration of 
its acid properties. This dephlogisticated marine acid, 
as its discoverer termed it, was examined by him with 
some precision, and many of its leading characters ascer- 
tained, especially its power of destroying colour, which 
has since rendered it of so much importance to the bleach- 
er. It has since been termed oxymnriatick acid, and 
more recently, chlorine. Besides the valuable facts to 
which I have now alluded, Scheele's Essay on Manga- 
nese contains others of considerable interest and impor- 
tance. There can be little doubt that he discovered azote 
about the same time as Dr. Rutherford. He obtained it 
by exposing compounds of sulphur, and the alcalies and 
earths, to confined portions of atmospherick air. He 
found a part was absorbed, and that the remainder, though 
not fixed air, was still incapable of supporting combus- 
tion. He went a step farther, and demonstrated the ex- 
istence of azote in the volatile alcali or ammonia, from 
which he obtained it by the action of certain compounds 
of manganese. 

For our knowledge of the method of obtaining tartarick 
and citrick acids in their pure state from tartar and lemon 
juice, we are also indebted to Scheele, and for a variety of 
curious and interesting documents relating to some of the 
metallick acids, and their combinations. A compound of 
one of the acids of arsenick and copper was particularly 
described by him, and recommended as a green pigment ; 
he prepared it by adding to a solution of blue vitriol, an 
alcaline solution of white arsenick. 



,gcT. v.] THIRD DISSERTATION. 99 

His chemical tracts on the nature and properties of milk, 
his observations on ether, on the preservation of vinegar, 
on Prussian blue, and on the nature of the acid matter in 
various fruits, are all entiled to the highest praise. A just 
notion of their excellence may be formed by comparing 
them with the essays of the ablest Chemists of the present 
day : in regard to experimental accuracy and just con- 
clusion, they generally stand this severe test; no small 
merit, when his humble means and deficient education are 
thrown into the balance against him. 

But, of the various works of Scheele, that which is most 
decidedly characteristick of an inventive and original ge- 
nius, is his Chemical Observations and Experiments on 
Air and Fire. Every page of this treatise has its merits, 
and they are distinct and peculiar ; sometimes we are 
struck with the sagacity of his inductions, at others, with 
the appropriateness of his experiments. The facts are 
detailed in intelligible, clear, and distinct arrangement; the 
theoretical speculations are adduced with that caution and 
modesty which ensures attention, and often commands ac- 
quiescence. Nor is this essay deficient in original dis- 
coveries of the highest class. He obtained oxygen from 
manganese without any knowledge of Priestley's prior 
claims ; he calls it empyreal air^ and has detailed its pro- 
perties and several modes of procuring it, with becoming 
accuracy and minuteness. Upon the composition of the 
atmosphere, and of metallick calces, he dwells at consi- 
derable length, and relates several remarkable facts con- 
cerning the chemical powers of the prismatick rays, and 
the radiation of terrestrial heat.^ 

^ In this admirable Dissertation, Scheele points out the dif- 
ference between the heat which radiates from a heated surface, 
and that which is dilTused by currents of hot air. He also 
shows, that terrestrial radiant heat does not pass through glass, 



100 THIRD DISSERTATION. [sect. v. 

From one who wrote in that twilight period, when 
chemical philosophy was emerging from errour and absur- 
dity, we are not to expect the logical accuracy required 
at the present day. Scheele is sometimes hasty, and oc- 
casionally unintelligible ; but seldom careless, and never 
ridiculous. Different men will form different estimates of 
Scheele's talents, and although I cannot agree with a con- 
temporary biographer who designates him " as the bright- 
est ornament of human nature, and the most extraordinary 
man that ever existed ;" it will, I think, be generally ad- 
mitted, that he was an acute and industrious philosopher, 
and an upright honourable man. 

Of the Chemical Philosophers that adorned the last 
age, the Honourable Henry Cavendish ^ stands foremost 
in the first rank. 

While Priestley and Scheele were extending the boun- 
daries of knowledge, and pursuing that brilliant career of 
which I have just presented an outline. Cavendish was 
not less successfully employed in another train of investi- 
gation. 

Van Helmont, Mayow, and Hales, had, by a series of 
crude and imperfect experiments, demonstrated the exist- 
ence of inflammable aeriform fluids ; but the nature of the 
peculiar principle to which they owe their inflammability 
had been but xery imperfectly ascertained, till Cavendish 
turned his mirtd to the subject, and published upon it 
in the Philosophical Transactions for 1776. The paper 
I allude to consists of three tracts, relating to inflammable, 
fixed, and nitrous air. The first is chiefly entitled to 

while that of the sun does ; that polished glass and metal re- 
flect both heat and light, but that both are absorbed by a surface 
covered with lamp black; and that the direction of radiant 
heat is not diverted by a current of air. 

* Born in London on the 10th of October 1731. -^ 



McT.v.] THIKD DlSSERTATrON. 101 

attention from its originality and importance ; in the others 
he had been anticipated by Majow and Black, or ex- 
celled by Priestley, Scheele, and others of his contempo- 
raries. 

By acting with dilute acids upon iron, zinc, and tin, 
Mr Cavendish obtained an inflammable elastick fluid. He 
found that it was afforded in the largest quantity by 
zinc, and that iron yielded more than tin ; and he particu- 
larly mentions, that the state of dilution, and quantity of 
the acid, provided it was sufficient to effect the solution 
of the metal, did not affect the quantity or quality of the 
air. He discovered in the gas thus obtained several cha- 
racters, which at once distinguished it from the other 
varieties of the air then known. It was not absorbable by 
water, it extinguished flame, and was fatal to animal life ; 
but, when a candle was presented to it, it inflamed ; and, 
when pure, burned with a blue lambent light. It was 
found to be the lightest known form of ponderable matter. 
Mr Cavendish considered it as about eleven times lighter 
than atmospherick air ; but subsequent experiments have 
shown that, when it is rendered perfectly dry, and col- 
lected in a state of purity, it is about thirteen times lighter 
than atmospherick air. Compared with oxygen or de- 
phlogisticated air, its relative weight is as 1 to 15. ' 

' This circumstance has led to its application for filling air 
balloons, which formerly were made to ascend by distension 
with rarefied air — a large quantity of fuel became thus iieces- 
sarjs which was greatly inconvenient on account of its weight ; 
and the flame required for the rarefaction of the air inclosed in 
the balloon, was dangerous in the extreme — by confining in- 
flammable air in a silk bag, of sufficient dimensions, its small 
gpecifick gravity enables it to float in our atmosphere. 'I'ije 
first ascent, with a balloon filled with hydrogen, was performed 
in France by M. Charles, on the 1st of December 1783 — he 
rose to the enormous heij^ht of 10,500 feet above the earth's 
surface. There is a passage in Dewyijt's Scnnons, published in 



102 THIRD DISSERTATION. [sect. v. 

He next proceeded to examine the results afforded by 
burning mixtures of inflammable and common air ; and 
found that, in the proportion of one part of the former to 
about three of the latter, the mixture exploded on the con- 
tact of flame ; and that, when the vessel in which this in- 
flammation was performed was previously dry, it always 
became moist after the explosion. 

This circumstance was noticed by Macquer in 1766, and 
shortly after by Priestley, but that water was the result 
of the combustion, seems first to have occurred to Mr. 
Watt, who suggested the idea to Dr. Priestley in 1783. 

In January 1784, Mr. Cavendish presented a paper to 
the Royal Society, entitled Experiments on Air^ in which, 
after some preliminary remarks, he adverts to Mr. Warl- 
tire's experiments, related by Dr. Priestley, upon the 
formation of dew during the combustion of inflammable 
with common air, which by that gentleman was referred 
to the deposition of the air's moisture during its phlogisti- 
cation ; for by the Chemists of that period, inflammable 
air seems to have been considered identical with phlogis- 
ton. 

The method in which Mr. Cavendish pursued this in- 
quiry was not less new than satisfactory, and the body of 
evidence adduced, so conclusive as to convince the most 
sceptical mind of the accuracy of his deductions. 

To ascertain the nature of the products of the combus- 
tion of inflammable air, he had recourse to two plans : he 
burned it slowly and rapidly, — in the one instance, a stream 
of the air issuing from a small tube, was inflamed in con- 
tact with the atmosphere, or oxygen ; in the other, the 
two gases were mixed, and suddenly detonated ; and he 

1658, from which it has been concluded, that balloons were 
known at that early period. 



SECT, v.] THIRD DISSERTATION. 103 

found that, proper precautions having been taken to ex- 
clude extraneous bodies, the result was perfectly pure 
water ; " it had no taste nor smell, and left no sensible sedi- 
ment when evaporated to dryness, neither did it yield any 
pungent smell during the evaporation ; in short, it seemed 
pure water."^ His grand discovery of the composition 
of water necessarily led to a variety of others, scarcely 
inferiour in importance, and it tended to the elucidation of 
a variety of intricate phenomena in nature and art, in 
which that universal fluid is concerned. It was verified 
and established by the analytick and synthetick research- 
es of many modern Chemists, and it became a great organ 
in subverting the phlogistick doctrine. 

In the synthetick experiments proving the composition 
of water, originally devised and executed by Cavendish, 
he frequently observed the production of acid matter ; the 
water formed was sour to the taste, and reddened vegeta- 
ble blues ; and he ascertained that these effects arose from 
the presence of a portion of nitrous acid. Whence this 
was derived remained to be proved, — whether the elements 
which, in one proportion, formed water, produced, in ano- 
ther proportion, the nitrick acid, or whether it resulted 
from other causes. In a paper read before the Royal So- 
ciety, in June 1785, Mr. Cavendish sets this curious and 
interesting question at rest, and developes the source of 
the acid which appeared in his former investigations. It 
arose from the presence of a portion of azote, which, when 
made to unite with oxygen, produced nitrick acid. The 
atmosphere has already been shown to consist of azote and 
oxygen, — these gases are there merely mechanically mix- 

^ Philos, Trans. 1784. p. 129. Inflammable air has since re- 
ceived the name hydros;€n, i. e. generator of water. 



104 THIRD DISSERTATION. [sbct. v. 

ed ; when they are made to combine in the presence of 
water, nitrick acid results. 

This curious fact was proved by several experiments. 
That which is most simple, and most satisfactory, consist- 
ed in confining a small portion of atmospherick air in a 
bent tube over quicksilver, and passing the electrick spark 
for some hours through the mixture. A diminution took 
place in its bulk, the mercury was corroded, and, on in- 
troducing a solution of potash, it became saturated, and 
yielded nitre on evaporation, a salt composed of potash 
and nitrick acid. 

These are the principal discoveries with which Caven- 
dish enriched the science of Chemistry ; they relate to 
the properties of hydrogen or inflammable air, to the com- 
position of water, and to the constitution of the nitrick 
acid. They are detailed in three communications to the 
Royal Society ; the first stands in the Philosophical 
Transactions for 1766 ; the other two in the volumes for 
1784 and 1785. 

Those who have heard Mr. Cavendish designated the 
Newton of Chemistry, and have only hastily perused his 
tracts, or witnessed imperfect illustrations of his research- 
es, may perhaps regard him less worthy that honourable 
and high distinction than his contemporaries Priestley and 
Scheele ; but a more careful examination of his writings, 
and a comparison of his reasoning and methods of research 
with those of even his most eminent fellow-labourers in 
science, will unanswerably support his claims, and display 
such peculiar and varied excellence, as must justify the 
highest encomiums and most elaborate eulogies which have 
been bestowed on his exalted name. In his philosophical 
proceedings, the severest scrutineer is challenged to de- 
tect a single false step, for every conclusion he has formed, 
every theory that he has advanced, even every sentence 



MCT. v.] THIRD DISSERTATION. 105 

he has written, will bear microscopick examination. Aware 
that there was no rojal road to philosophick truth, he re- 
lied solely upon the light of experiment, in the path of in- 
duction, and from this he never deviates. If he excelled 
not his contemporaries in the number of his discoveries, 
he certainly equalled them in their importance, and went 
far before them in statical accuracy and mathematical pre- 
cision : but as a Philosopher he scarcely admits of compari- 
son ; in him most of the defects of his contemporaries 
were absent, and their talents concentrated ; he was "him- 
self alone." In Cavendish science may boast of a fol- 
lower not less disinterested than successful : his affluence 
was princely, and his family noble ; it was therefore not 
the desire of distinction in society, nor the more imperious 
call of necessity, but the thirst for knowledge, and love 
of truth, that summoned him to her banners. 

Mr. Cavendish did not lisp in the language of science ; 
it was, indeed, late before he appeared as a candidate for 
philosophick fame. His first paper was published in the 
Transactions of the Royal Society for 1766, when he was 
in his 36th year, a period of life at which Black, Priestley, 
and Scheele, had already acquired no inconsiderable ce- 
lebrity. He was not confined to Chemistry only ; Elec- 
tricity, and subjects connected with Meteorology and As- 
tronomy, often occupied his thoughts and employed his 
pen : his last essay is on the division of astronomical in- 
struments, published in the Philosophical Transactions 
for 1809. He was then in his 78th year, and in full pos- 
session of bodily activity and mental energy. After a 
few days illness, he expired on the 4th of February 1810, 
in the 79th year of his age. 

In private life, he was unambitious, unassuming, bash- 
ful, and reserved : he was peevishly impatient of the in- 
conveniences of eminence ; he detested flattery, and was 

11 



106 THJRD DISSERTATION. [sect. v. 

uneasy under merited praise ; he, therefore, shunned gene- 
ral society, and was only familiar in a very limited circle 
of friends. Here he bore his great faculties always meek- 
ly : his conversation was lively, varied, and instructive ; 
upon all subjects of science he was at once luminous and 
profound ; and in discussion, wonderfully acute. 

We are now about to enter upon that period of our his- 
tory at which the science was reformed and modified by the 
French school. Of this chemical revolution I shall en- 
deavour to present a faithful though faint outline. I shall 
attempt to show the grounds of innovation, to expose the 
weak parts of the plan, to exhibit its merits, and to com- 
pare it with former theories. In the meantime, it may not 
be improper to take a rapid survey of the ground we have 
gone over, and to enumerate the materials already in the 
hands of the reformers. 

In the early hypotheses respecting the phenomena of 
combustion, tbey were conceived to depend upon the sepa- 
ration of a peculiar principle, called by Stahl and his as- 
sociates Phlogiston ; but the fallacy of these views was 
shown by Mayow, who, with his predecessor Rey, de- 
monstrated Ihe necessity of atmospherick air in the pro- 
cess. The attention of Chemists was drawn from these 
subjects early in the eighteenth century, by the new train 
of investigation in which Dr. Black had successfully em- 
barked, and the field of Pneumatick Chemistry, which 
was so eminently cultivated by Priestley, Scheele, and 
Cavendish, absorbed universal attention. 

The ideas of the ancients concerning the Elements 
were now completely subverted. The air we breathe was 
proved to consist of two distinct aeriform fluids — the one 
a powerful supporter of combustion and respiration, the 
other extinguishing flame and exterminating life. Water, 
so long considered as a primiti\ e body, had been resolved 



sEcT.vi.] THIRD DISSERTATION. 107 

into simpler forms of matter; in short, novelties of the 
most attractive kind presented themselves on every side. 

The discovery of hydrogen was seized upon by the ad- 
vocates of phlogiston, as supporting their hypothesis, and 
it was generally considered as identical with that sub- 
stance, which had long been hypothetical, but was now ex- 
hibited in a tangible form. The reduction of the raetal- 
Jick calces, by hydrogen, was considered as a powerful 
argument in favour of these notions, and wherever phlogis- 
ton had been supposed to be absorbed or evolved, hy- 
drogen seemed to play the part of that imaginary princi- 
ple. 

The views of Priestley and Scheele were combated by 
a host of petty controversialists, whose names are yet ex- 
tant, but whose writings are sunk into oblivion — they 
brought into the field an army of words, but not a single 
observation, founded upon fact or experiment. Mr. Cav- 
endish was more strenuously and respectably opposed ; 
among those who stood up against his theoretical views, 
Mr. Kirwan deserves especial mention, for he laid other 
departments of Chemistry under considerable obligations ; 
but his arguments and learning were of little avail against 
the tried and sterling facts which he questioned ; they are 
no creditable records to the author, but serve to show the 
feebleness of subtilty when opposed to the strength of 
truth. 



SECTION VI. 

INVESTIGATIONS OF LAVOISIER. 



Among the eminent scientifick characters who adorned 
the last century, Lavoisier has always been looked upon 



108 THIRD DISSERTATION. [sect. vi. 

with high consideration. That his talents were shining, 
and his career brilliant, cannot be denied ; but that he has 
those high claims to originality which we have been obliged 
to allow his exalted rivals, has been doubted by the ge- 
nerality of historians, and denied by those who have had 
access to the most correct information. I shall briefly no- 
tice his most important investigations, and afterward endea- 
vour to sketch his character as a Philosopher. 

The phenomena of combustion were with Lavoisier, as 
with his predecessors in the field of theoretical chemistry, 
a leading object of attention ; and the theory of latent heat, 
devised by Dr. Black, was assumed as the ground-work of 
his new views. 

It has already been stated, that, during the conversion 
of solids into fluids, and of fluids into vapours, there is a 
considerable absorption of heat ; and that, on the other 
hand, when vapours and liquids are restored to the fluid 
and solid form, the heat, which they contained, is evolved, 
or passes from the latent to the sensible or thermometrick 
state. These views were assumed by the French school 
.as the basis of their theory of combustion, The gas call- 
ed by Priestley dephlogisticated air, and by Lavoisier oxy- 
gen, was regarded as a compound of a peculiar ponderable 
basis, united to the matter of light and heat. During the 
process of combustion, the basis was represented as com- 
bining with the combustible, augmenting its weight, and 
changing its properties ; whilst the imponderable elements 
of the gas, the light and heat, were said to be developed 
in the form of flame. 

Lavoisier instituted an extended and beautiful series of 
researches connected with this subject. Dr. Ingenhouz 
had devised the brilliant experiment of burning iron wire 
in oxygen, but had neglected any inquiry into the change 
suffered by the gas and the metal. Lavoisier ascertained 



SECT. VI.] THIRD DISSERTATION. 109 

that the iron was converted into the black brittle sub- 
stance, called martial ethiops by the old chemists, and 
that 100 grains of iron absorbed about 100 cubical inches 
of the gas, and increased 33 grains in weight. Hence 
martial ethiops appeared to be a compound of oxygen and 
iron. 

Phosphorus was burned in the same manner. There 
was a considerable absorption of the gas, and it appeared 
that the phosphorus had sustained a precisely equivalent 
increase of weight. 

The general conclusions deduced from these experi- 
ments were bold, but incorrect. It was assumed that oxy- 
gen must be present in all cases of combustion ; that the 
base of the gas always unites to the burning body, and 
that the heat and light essential to the aeriform state of 
the oxygen are consequently thrown off, or rendered sen- 
sible. With regard to the necessity of the presence of 
oxygen, it may be remarked, that the cases are very 
numerous, in which bodies burn, and vividly too, indepen- 
dent of that principle, although it is perfectly true that, 
in the generality of instances, oxygen feeds the flame. 

It is, therefore, more philosophical, to consider combus- 
tion, or the evolution of heat and light, as a general re- 
sult of intense chemical action, and as ensuing in all cases 
where it may be conceived that the corpuscles of bodies 
are thrown into violent motion, than as depending upon 
the presence of any distinct substance, or ensuing from 
the mutual actions of any appropriate forms of matter. 

But farther ; there are many cases in which oxygen 
unites to bodies, without the evolution of heat and light, 
as during the gradual change of some of the metals by ex- 
posure to air. And there are numerous instances in 
which vehement combustion ensues, not only where there 
is no condensation of air, but where gaseous matter is 



110 THIRD DISSERTATION. [sect. yi. 

positively produced, as in the inflammation of gunpowder ; 
and hence the theory of latent heat, as applied to the 
composition of gases, is insuflScient to account for the 
phenomena. 

Another weak part of the French hypothesis is that 
relating (o the evolution of light, which, if derived from 
the gas, should be proportional to its consumption or soli- 
dification, whereas it depends chiefly on the combusti- 
ble. Richter, Delametherie, and Gren, regarded the gas 
as ^affording the heat only, which is proportional to the 
quantity consumed ; and they supposed the evolution of 
light to be derived from the combustible, and several 
modern chemists have espoused this explanation. Phos- 
phorus emits much more light than hydrogen, but con- 
sumes less oxygen ; hence we should regard phosphorus, 
as containing more combined light than hydrogen. This 
hypothesis involves several unnecessary suppositions ; but 
these cannot be discussed without reference to subjects 
which are excluded by the limits of this discourse. It 
may, however, here be observed, how nearly the French 
theory of combustion agrees with that of Rey and Mayow, 
in referring the increase of weight of the combustible, to 
the fixation of air : this was the great obstacle in the phlo- 
o-istick hypothesis, and Rey and Lavoisier overcame it by 
the same means. 

Oxygen was not merely considered by the French 
school as necessary to combustion, but also as an essen- 
tial ingredient in all acids (whence the term oxygen ;) but 
there are many acids in which no oxygen can be proved 
to exist, and it is now known even to form a component 
part of the alcalies and earths. If sulphur be burned in 
oxygen, it produces sulphurous acid gas : if potassium 
be heated in sulphurous acid gas, it robs the sulphur of its 
oxygen, and is converted into potash ; here oxygen is seen 



SECT, vi] THIRD DISSERTATION. HI 

alternately producing an acid and an alcali, — the result 
depending not upon the oxjgen, but upon the base with 
which it combines. 

In detailing the discoveries of Dr. Black, I was led to 
notice his researches concerning the production of fixed 
air. This gas was also examined with much attention by 
Priestley, Scheele, and Cavendish, and they have each 
made important additions to our knowledge of its sources 
and properties. 

Lavoisier's inquiries respecting the composition of fixed 
air, and its production during the combustion of charcoal 
and of the diamond, were highly important as connected 
with his general theoretical views. Black had indeed as- 
certained that burning charcoal produced fixed air, but 
rested satisfied with the mere fact, and pursued not the in- 
quiry which is naturally suggested, and which was eager- 
ly taken up by Lavoisier at an early period of his scien- 
tifick career. He burned a given weight of charcoal in a 
given proportion of oxygen gas confined over quicksilver, 
and when the vessel had cooled, he introduced a solution 
of potash, which absorbed the fixed air. He thus ascer- 
tained the bulk of the fixed air generated by the charcoal, 
and the bulk of oxygen consumed ; and, by weighing the 
residuum of the charcoal, he found the quantity lost by 
its combustion. From such experiments, he was led to 
regard fixed air as composed of oxygen and charcoal, in 
the proportions by weight of about 70 of the former and 
30 of the latter. Soon after the discovery of fixed air by 
Black, it was demonstrated by Keir, Bergman, and Fon- 
tana, to possess acid properties ; hence it was occasion- 
ally termed aerial acid, cretaceous acid, and mephitick 
acid. Consistently with the principles of the new nomen- 
clature, it received from Lavoisier the name of carbonick 



112 THIRD DISSERTATION, [sect. ti. 

acid, a term implying that it is composed of charcoal and 
oxygen ; and this it has since retained. 

The production of fixed air, or, as we may now call it, 
carbonick acid, during the combustion of diamond, is one 
of the most remarkable and important discoveries with 
which Lavoisier enriched chemical science. The destruc- 
tion of this precious gem by fire was demonstrated by the 
Florentine academicians as early as 1690; they exposed 
a diamond to the focus of a burning lens, and found that 
it was entirely evaporated ; and Francis the First, of Ger- 
many, witnessed the same phenomenon in the heat of a 
furnace. Lavoisier proved that the diamond underwent 
no change when air was excluded ; and that, when ignited 
in oxygen gas, it produced carbonick acid ; whence the 
inevitable conclusion that the diamond and charcoal are 
identical in their nature ; and that the vast difference in 
their appearance and mechanical qualities is the result of 
aggregation ; that the one is crystallized, the other in a 
less indurate form. Unprecedented as such an idea may 
seem, it is not only warranted by the experiments of La- 
voisier and others, but also in some degree supported by 
analogy. Thus, when argillaceous earth, which is a white 
pulverulent substance, is aggregated by mechanical at- 
traction info a crystaline form, it constitutes the sap- 
phire, one of the hardest and least destructible of the 
gems. In one state, the earth is soft, and readily soluble 
in acids ; in the other, its insolubility equals its induration : 
but there is one invincible anomaly relating to the conduct- 
ing power of the diamond and charcoal, in regard to elec- 
tricity ; the former ranks among the non-conductors, the 
latter is a conductor ; -and hitherto mechanical texture has 
not been shown, in any analogous cases, to interfere with 
the power of conducting electricity. 



^luvi^ THIRD DISSERTATION. 113 

Among those who have further explored the phenome- 
na of the combustion of the diamond, and who have veri- 
fied and extended the original views of Lavoisier, we find 
the names of the most eminent European Philosophers. 
Few subjects in Chemistry have been so eagerly pursued, 
and the united results of different experimentalists have 
rarely tallied with the precision which these researches 
present.' 

The discoveries of Rutherford and of Priestley, in the 
years 1772 and 1774, had disclosed the elements of atmos- 
pherick air, and several experiments respecting the pro- 
portions in which they are blended, had been instituted by 
these, and other Philosophers. In the year 1775, Lavoi- 
sier resumed these inquiries, with a masterly and decisive 
hand ; he heated mercury in contact with a known portion 
of atmospherick air; it gradually acquired a red film, 
which after some days ceased to form, and the metal remain- 
ed unaltered ; he then withdrew the fire, and suffered the 

' That the quantity ol* carhonick acid, afforded by a ^iven 
weight of diamond, is the same as that yielded by a similar qii^n- 
tity of charcoal, is the great proof of the identity of those ap- 
parently dissimilar substances : this was dt moustrated in the 
year 1796, by the retined and elegant experiments of Mr. T n- 
nant, whose untimely loss society has lately had to de[)l<.re, 
Mr. Tennant was a profound philosopher, and a matchless 
companion, — his learning was without pedantry ; his wit with- 
out sarcasm, — he was deep, but always clear; gentle, bnt never 
dull. To those who knew him not, it is scarcely possible to 
offer an adequate representation of his singulnrly pleasint^* and 
enlightened character, — by those who enjoyed his acquaintance, 
and partook of his social hours, his extent of kno\vled2:e, his 
happy and unrivalled talent for conversation, his harmless but 
brilliant flaslies of merriment, and all his amiable peculiarities, 
can never be forii;otten. Friendship will long continue to weep 
over his srave, and science to lament beside his tomb. 

Mr. Tennant was born in Yorkshire in 1761, and died at 
Boulogne in 1815. 

See Biographical Account of Smithsou Tennant, Esq. in 
Thomson's Annals of Philosophy^ Vol. VI. 

15 



114 THIRD DISSERTATION. [sect, v: 

vessels to cool ; be found that the air had diminished in bulk, 
and that the quicksilver had increased in weight ; that the 
loss of the former was equivalent to the gain of the latter 
— which had absorbed the oxygen of the air, leaving the 
azote unaltered. By such investigations he arrived, with 
tolerable precision, at the proportion in which these gases 
exist in common air, and found, that, by mixing forty-two 
parts, by measure, of azote, with eight parts, by measure, 
of oxygen, he produced a compound precisely resembling 
our atmosphere, in its power of supporting combustion and 
respiration, and of contributing to the calcination of the 
metals. 

Besides these researches and discoveries, Lavoisier was 
the author of many scientiiSck papers in the Memoirs of 
the Parisian Academy. Of these a brief and hasty no- 
tice will suffice, as they relate not to the great reform of 
chemical theory, in which he was so conspicuous an actor, 
and upon which his fame and reputation have chiefly 
been raised. 

In 1764, the French Government proposed, as a prize 
question, *' Which is the best method of illuminating the 
streets of a large metropolis ?" It was answered by La- 
voisier ; and he was rewarded with an honorary medaK 
In 176B, he became a member of the Academy. In 1770, 
he controverted a prevailing opinion respecting the con- 
vertibility of water into earth; and, two years afterwards, 
published an ingenious geological essay upon the changes 
and stratification of the globe. In 1774, he entered upon 
the grand field of discovery wliich has occupied so much 
of our attention, and published an ingenious and compre- 
hensive view of Pnejimatick Chemistry. A few years 
afterwards, his theory of acidity, of combustion, and of 
oxidizement; his experiments upon the composition of 
water, and of the atmosphere, and his views respecting the 



SECT. VI.] THIRD DISSERTATION. 115 

nature and affections of heat, were successively presented 
to the publick ; and, in 1789, his work entitled Elemens de 
Chimie was given to the world. It contains a full account 
of his theoretical views and experimental researches. 

Lavoisier was an earnest promoter of the Chemistry of 
the Arts. He turned his attention to the improvement of 
several manufac lures, and his labours were rewarded by 
considerable success. Agriculture was with him a favour- 
ite pursuit, and he endeavoured to improve its processes 
by experimental research. He was an able Political Eco« 
nomist ; and, for a few years, filled the oflSce of a Com- 
missioner of the National Treasury, with honour to him- 
self, and benefit to his country. 

The moral and social character of Lavoisier was of the 
most estimable cast. Contemporary historians agree in 
eulogizing his mild, amiable, and obliging manners; in ex- 
tolling his liberality, and in praising him, as the encoura- 
ger of deserving ingenuity, and the ardent patron of science 
and the arts. 

Through the scenes of the Revolution, such a man 
could not expect to pass unmolested. He was rich, and 
therefore criminal; virtuous, and consequently offensive. 
In short, because his publick character and private life 
were equally unimpeachable and blameless, he was mark- 
ed out for destruction, and murdered upon the scaffold on 
the 8th of May 1794, in his native city of Paris, and in 
the ,01st year of his age. 

Upon these acts of iniquitous barbarity and inhuman 
treachery, equally degrading to the individual performers 
and to the beholding nation, it is neither my business nor 
inclination to dwell ; the recital of particulars would excite 
disgust rather than interest ; and would rather shock than 
inform. 

We must now divest ourselves of the impressions natu- 
ally arising out of the virtues, the eminence, and the mis- 



116 THIRD DISSEKTATION. [sEct.rr. 

fortunes of Lavoisier, and with unmixed attention steadily 
reflect upon his philosophical character. By some he has 
been extolled as the most original, inventive, and exalted 
genius of his age ; by others stigmatized as an universal 
and dishonourable plagiarist ; but these are the extremes of 
panegyrick and malevolence, each equidistant from can- 
dour and from truth. He was doubtless an acute, saga- 
cious, and useful Philosopher ; his zeal for the welfare of 
science was unremitting and exemplary, and his affluence 
enabled him to pursue it upon an extensive and splendid 
scale. As an original discoverer, he bends before Black 
and Priestley, and was inferiour to Cavendish and Scheele ; 
but, as a theorist, he has few equals ; be was com- 
prehensive, successful, and clear. If time has shaken his 
opinions, and loosened his speculations, the change must 
be referred to the imperfect and progressive state of 
ChemTstry, ralher than to their inherent futility. In Na- 
tural Philosophy, the systems of Pythagoras, Ptolemy, 
Descartes, and others, have successfully yielded to the 
satisfactory and apparently stable simplicity of the New- 
tonian doctrines ; but the Newton of Chemistry is yet to 
come. 

It must be regretted, that those who have censured lia- 
voisier with the uncandid and unacknowledged appropria- 
tion of the thoughts of others, have some grounds for 
the accusation. In bringing forward his theory of combus- 
tion, why did he smother the lucid opinions of Rey and 
Mayow ? why refuse praise and acknowledgments to Black, 
and Scheele, and Cavendish ? or, why appropriate the dis- 
covery of oxygen, in the face of the prior, indisputable 
and known claims of his friend and contemporary Priest- 
ley ? These are questions we cannot now answer ; but, 
those who have grounded harsh, indiscriminate, and se- 
vere censure, upon such accusations, have neither been 
animated by the independent spirit of true philosophy^ 



8BCT.VJ.] THIRD DISSERTATION. 117 

nor guided by the unbiassed love of truth. It must be reoiem- 
bered, that Lavoisier was never fairly confronted by these 
rivals and antagonists ; that unintentional inadvertency 
often accompanies scientifick ardour 5 that, in the eagerness 
of pursuit, he may have neglected that which, in a calmer 
hour, he would have seen, regretted, and acknowledged ; 
and that, in the hurry of discussion and heat of contio 
versy, he was suddenly summoned to eternity/ 

Though these considerations do not exculpate our phi- 
losopher, they must be allowed to extenuate his imputed 

^ Since writing the above, I have seen two scarce volumea of 
the posthumous works of Lavoisier in Mr. Hatciiett's library at 
Roehampton. They consist, in great measure, of extracts 
from, and sketches of his different papers read before the Royal 
Academy of Sciences, but several original Observations and 
Essays are also dispersed among them. They, in some degree, 
justify the observation which I have made in the text, that, had 
Lavoisier lived, he would have done merited justice to his pre- 
decessors and contemporaries, for he candidly reviews their opi- 
nions, and compares them with his own; at the same time, the 
following passage cannot be regarded as |}ertectly candid towards 
Rey, who, as 1 have shown above, founded his arguments 
not upon hypothesis, but upon experiment. 

I insert a long quotation, that there may be no misunderstand- 
ing upon the subject. 

After stating the prevailing phlogistick notions entertained 
at that period, he [)roceed3 as follows: '' Tel etoit I'etat des 
connoissances, lorsqn'uiie suite d'expcriences, entreprises en 
1772 sur les differentes especes d'air, ou de gaz qui se def^a- 
gent dans les elfervescences et dans un grand nombre d'ope- 
rations chimiques, me tireiU connoitre, d'une maniere demon- 
strative, quelle etoit la cause de Tauomentation de poids, qu'ac- 
qiiierent les metaux lorsqu'on les expose a Tuction du feu. — 
J'ignorois alorsceque Jean Rey avoit ecrit a ce sujet en 1630: 
et quand je Taurois connu, je n'aurois pu regarder son 0[)inion 
a cet eo;ard, que comme une assertion vague, propre a faire hon- 
neur au genie de Tauteur, m.iis qui ne disf)ensair pas les chimistes 
de constater la verilc de son opinion par des experiences. J'e- 
toisjejme,j'etoi3 nouvellement entre dans la carriere des sciences, 
j'etois avide de gloire, et Je crus devoir prenche quelques precau 
tions pour m'assurcria i>ro()riete de ma decouverte. 11 y avoit a 
cette epoque, une correspondance habituelle entre les savans de 
France -et ceux d'Angleterre; il reguoit entre les deux nations. 



318 THIRD DISSERTATION, [sfxt. v,5 

failings — they should induce us rather to soften the asperi- 
ties of his scientifick character, than to magnify its faults 
— instead of rejoicing that he was not perfect, we should 

une sorte de rivalite qui donnoit de I'importance aux experien- 
ces nouvelles, et qui portoit quelquefois !es ecrivains de Tune ou 
de J'autre nation, a les contester a leur veritable auteur; Je crus 
done devoir deposer, le V^ Novemhre 1772. Tecrit suivant cach- 
ete, entre les miinsdu Secretaire de I'Academie. Ce depot a 
ete ouvert a la seance du 5"*^ Mai suivant, et mention du tout a 
ete faite en tete de I'ecrit. 11 etoit concu en ces termes : — 

" II y'a environ huit jours que j'ai decouvert, que le soufre en 
bruiant, loin de perdre de son poids, en acquieroit au contraire j 
c'est a dire, que d'une livre de soufre, on pouvoit retirer beau- 
coup plus d'une livre d'acide vitriolique, abstraction faite de 
Thumidite de fair; il en est du m^me du phosphore : celte aug- 
mentation de poids vient d'une quantite prodigieuse d'air qui se 
fixe pendant la combustion, et qui se combine avec les vapeurs. 

'' Cette decouverte que j'ai constalee par des experiences que 
je regarde comme deeisives, m'a fait penser que ce qui s'ob- 
servoit dans la combustion du soufre et du phosphore, pouvoii 
bien avoir lieu a I'egard de tous les corps qui acquierent du 
poids par la combustion et la calcination : et je me suis per- 
suade, que I'augmentation be poids des chaux metalliques, tenoit 
a la meme cause. L'experience a complettement confirme 
mes conjectures : j'ai fait la reduction de la lithrege dans 
des vaisseaux fermes, avec I'appareil de Bales, et j'ai ob- 
serve qu'il se degageoit, au moment du passage de la chaux en 
metal, une quantite considerable d'air, et que cet air formoit un 
volume au moins mille fois plus grand que la quantite de li- 
tharge employee. Cette decouverte me paroissant une des plus 
interessantes qui ait ete faite depuis Stabl, J'ai cru devoir m'en 
assurer la pro[)riete, en faisant le present dejiot entre le mains 
du Secretaire de PAcademie, j)Our demeuier secret jusqu'au mo- 
ment ou je publicrai mes experiences." 

(Signe) " Lavoisier." 

"En rapprocbant cette premiere notice de celle que j'avois de- 
posee a I'Academie le 20'"^ Octobre precedent, sur la combustion 
du phos[)hore, du memoire que j'ai lu a I'Academie a sa seance 
publique de Pa^jues 1773, enfin, de ceuxque j'ai successivement 
publics, il est aise de voir,que j'avois concu des 1772, tout I'ensem- 
ble du systeme que j'ai public depuis sur la combustion. Cette 
theoriea laquelle j'ai donnede nombreux developpemensen 1 777, 
et que j'ai porte, presque des cette epoque a I etat ou elle est au- 
jourdhui, n'a commence a etre ensi2:nee par Fourcroy, que dans 
Thyver del786a 1787; elle n'a ete adoptee par Guyton Mor- 
veau, qu'a une epoque posterieure ; enfin, en 1785 Berthollet 
ecrivoit encore dans le systeme du phlogistique. Cette theorie 



sircT.vi] THIRD DISSERTATION. 119 

delight in his excellence, and should estimate his charac- 
ter as a Philosopher, not so much by the means he em^ 
ployed, as by the noble effects produced. 

Among many other subjects which engaged the atten- 
Hon of Lavoisier and his associates, that of reforming the 
nomenclature of Chemistry deserves to be noticed as 
highly beneficial to the promotion of the science, and as 
tending materially to facilitate its acquisition. I am in- 
clined, however, to think that, upon this point, too much 
credit has been given to the French school ; rage for in- 
Bovation, and not zeal for improvement, seems often to 
have guided the undertaking ; and terms, once deemed 
faultless, now appear not less absurd and objectionable 
than the fanciful names employed by the alchemical wri- 
ters. 

As principals in the formation of the new nomenclature^ 
we find the names of Guyton Morveau ^ and Fourcroy, two 
men who may certainly be considered as ornaments of their 
age and country. The former, amidst varied avocations, 
prosecuted Chemistry with successful diligence, and, had 
he given nothing else to the science, his name deserves 
to be transmitted to posterity, as the inventor of the means 
of destroying infection by acid vapours, the ejflicacy of 
which he first pointed out in the year 1773. His first 
essay on the reform of nomenclature was published in the 
Journal de Physique for May, 1782, and although it was 
strenuously opposed by the colossal power of the Royal 
Academy of Paris, the plan was not only afterwards ap- 
proved, but prosecuted by the eminent Chemists of that 
metropolis. The different papers and correspondence re- 

f{^cst done pas, commc je VcnUmLs dire, la tUonc dcs Chimistcs 
Francois: elk est la mimnc^ et c'est une proprieie qucjenxlame 
aupres de mes conttmporains ^iile la posterile." 

'Born at Dijon in 1737. Died at paris in 1815. See L;/^ 
by Ur. Granville la the Journal of Science and Arts, Vol. 111. 



120 THIRD DISSERTATION. [skct. n, 

lating to this subject are in many respects, curious and 
interesting from the difference of opinion which prevailed 
respecling the terms he adopted, and the ultimate benefit 
Jikelj to result from the reformation. 

Fourcroj'i is a well known name in the chemical world ; 
his works rank among the most celebrated which France 
has produced in the science of Chemistry, though they 
are sometimes deficient in candour, and sometimes in cor- 
rectness. His labours were important, and his discove- 
ries numerous, but they are in many respects, so closely 
interwoven with those of contemporary Philosophers, that 
I have deemed it expedient to wave farther notice re- 
specting their objects and merits. 

I hare now brought my narrative to the conclusion of 
the last century, about which period Electricity began 
to assume importance as a chemical agent, and the Vol- 
taick apparatus became a necessary implement of the la- 
boratory. To this source, the new aspect which chemical 
science now wears, may principally be referred, and the 
historian, who shall in aftertimes record the advances that 
have been made in Chemistry during the last eighteen' 
years, will excite triumphs of the human mind never ex- 
celled, and rarely equalled. -^ — I am apprehensive that the 
inquisitive eye will delect several omissions in the fore- 
going pages, although I have dtligenlly endeavoured to 
record every important event in the general history of the 
science. Of many who have attained deserved eminence 
in the exclusive pursuit of its distinct branches, no men- 
tion has been made : I have looked with attention into 
their works, and am well aware of their individual merits ; 
but I should have swerved from the principal object of 
this Dissertation, that of recording discoveries, had I at- 
tempted even the superficial enumeration of their infinite- 
ly varied applications. 

' Born in Paris in 1755, where he died in 1809. 



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